Suppose apples sell X boxes, and oranges also sell X boxes according to the meaning of the question. Make an equation.

( 156-x)=(8+ 1)(84-x)

solve

156-x=9(84-x)

156-x=756-9x

9x-x=756- 156

8x=600

The solution is x=600/8=75.

75 boxes of apples and 75 boxes of oranges were sold.