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= 24. While S6 subtracts the equation p + l = 60 with
p - l = 12, and the result obtained is l = 24. To obtain
a p-value, he substitutes the value of l = 24 in the
equation p + l = 60, thus obtaining p = 36
Figure 7: Solve the problem with subtraction.
From the way of S1, S2, S5, and S6, the researcher
sees that the concept of finding the value of p in l is
the same, but there are differences in the procedure.
The difference in procedure shows the creative
thinking of each subject in solving problems.
3.2.2 Guessing
There are 2 subjects i.e. S3 and S4 have different
ways of finding p and l values. S3 writes in the form
of the equation L = p + p + l = 96 cm and L = p + l +
l = 84 cm and makes a guess by taking the value p =
36, l = 24. In Figure 8 below, shows that S3 replaces
the value of p = 36, l = 24 to equation 2p + l = 96 and
equation p + 2l = 84 so that the equation becomes true
(the value on the right-hand side is the same as the
value on the left-hand segment. From the interviews,
it is obtained that S3 takes p-value = 36, l = 24 by
"guessing." Although "guessing" is one of the
strategies for solving problems, it needs mathematical
argumentation to strengthen the validation of the
alleged/guessed evidence. While S4 has a different
way with S3. S4 adds the equation 2p + l = 96 with
the equation p + 2l = 84. From the sum, he got the
value on the right-hand side which is 180, then he
calculated 180 ÷ 3 = 60. From the results obtained,
then he calculated 96 - 60 = 36, and he obtains a value
of p = 36. The process performed by S4 in making
mathematically incorrect allegations. Next, to obtain
a value of l, S4 subtracts the equation 2p + l = 96 with
the equation p + 2l = 84. The result obtained in the
process is l = 24.
Figure 8: Guessing based category.
From the process carried out by S3 and S4 in Figure
8, the researcher saw that the two subjects did not
have an initial plan to find the length and width on
the surface of the blackboard. However, both
subjects have good ability to make guesses even
though they cannot provide mathematical
arguments to strengthen the validation of such
alleged evidence
3.3 Use Predefined Concepts to Resolve
the Issue
From the result of the work and the interview result,
it was found that all subjects knew that the formula
for the area of the rectangle is p × l. From the results
obtained, where p = 36 and l = 24, the six subjects
substitute into the formula and obtain the area of the
rectangle. From the results of the work, S1 and S2
obtained 864 cm2, S3 obtained 864 cm, S4, S5, and
S6 obtained 864. From the calculation of 36 × 24, all
subjects who answered correctly that 864. S3, S4, S5,
and S6 did not know by both that the unit area of the
rectangle is centimeter squared (cm
2
).
4 DISCUSSION
In building an understanding of the problem, there is
a tendency that deaf students illustrate the problem in
the form of images. Illustrating the problem in the
form of images shows that the thought process
constructed by the subject starts from the semi-
concrete to the abstract. Deaf students find it easier to
understand the problem if the problem presented in
Visual form is very beneficial for a deaf student
(Frostad, 1999). In addition, illustrating in the form of
images is the best mathematical ability possessed by
deaf students (Nunes, 2004). To solve the given
problem, there are two categories of ways done by the
six subjects to say and guess.
Summing up is counting one by one. Deaf student
performs oral calculations and written calculations
using sign language which is a simple arithmetic skill
possessed by a deaf student (Merrienboer, 2005).
Limitations do not become an obstacle to the six
subjects in doing the exploits through images, doing
algebraic engineering by summing and subtracting
the equations that have been obtained. The way in
which the subjects are used is not one of the methods
taught in solving the two-variable linear equation
system. This way arises as a result of the creative
thinking by the subject and also because of the
knowledge that has been stored in the form of a
schema in long-term memory, not from its ability to
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