The objective of this research was to identify the students' levels on
algebraic reasoning; they were the tenth grade students of TKR-T SMK
Muhammadiyah 2 Ajibarang. It was a qualitative descriptive research. The
research subjects were students of 10th grade of TKR-T SMK Muhammadiyah 2
Ajibarang; they were selected using purposive sampling. Data were collected by
testing, interviewing and recording. Based on the achievement score of final
semester examination in 2017/2018 academic year, the students were grouped
into three groups namely high, medium and low category. Three students were
selected from each group to be respondents. The results showed that high
achievement group did not fully comprehend level 4 yet (changing numeric
numbers into parameters), whereas the students were able to comprehend level 5
(operating two or more parameters) and level 6 (proving mathematical formulas
with certain requirement). For the medium achievement group, the results showed
that students did not fully comprehend level 4 (changing numeric numbers into
parameters), whereas some students fully comprehend level 5 (operating two or
more parameters) and level 6 (proving mathematical formulas with certain
requirement). Meanwhile, for the low achievement group, the results showed that
students did not comprehend level 4 (changing numeric numbers into
parameters), level 5 (operating two or more parameters) and level 6 (proving
mathematical formulas with certain requirement).