Answer:
the scores on her last test is x (x > 0)
because on her last tests she scored 4 points lower than she did on her fifth test
=> the scores in the 5th test is x + 4
because Angela’s average for six math tests is 87, we have:

=> on her last test, she had 85
=> on her 5th test, she had 85 + 4 = 89