3. Justine took a pre-test and post-test to measure his proficiency in Math. His score in
the pre-test was 90 and his score in the post test was n. If the average of the two tests is 91,
what is an equation that can be used to solve for his post-test score?
a. 90+n= 91
2
b. 91+ = 90
2
c. 90-n = 91
2
d. 91-n = 90
2​