Answer:
93
Step-by-step explanation:
Setup an equation. Add the 5 tests together, the unknown test will be represented by x, Since there are 5 tests total, you will divide by 5. to find the average.
To solve first multiply both side by 5.
Add the left side and then solve for x
Subtract 357 from both sides
357 - 357 + x = 450 - 357
x = 93
The last test has to be a score of 93 to get an average of 90.