Answer:
90 minutes (1 hour and 30 minutes)
Explanation:
Using cross-multiplication, I wrote down the equation 8 tests / 10 mins = 72 tests / x minutes. After cross multiplying, you'd get 720 = 8x. To get the answer, you'd then divide 8x and 720 by 8 to isolate the x, wounding up with 90 minutes.
Hope this helped!