Answer:
31 tests.
Step-by-step explanation:
The rate for the grading is 10.5 every 30 minutes.
Two 45 minute prep periods are 90 minutes.
90 / 30 = 3.
Since three 30 minute periods fit into 90 minutes, we get
3 x 10.5 = 31.5 tests.
Since a teacher did not finish grading the .5 of the test, we don't count it.
Our answer is 31 tests.
