Answer:
79+94+91+92+test5)/5=90
The lowest score have to be 94
Explanation:
Our goal is gona be to have an average of 90, it can be higher but we are going to use this.
For average the equation is
(test1+test2+test3+test4+test5)/5=average
We know the result for the first 4 tests
Test 1=79
Test 2=94
Test 3=91
Test 4=92
But we dont know test 5
(79+94+91+92+test5)/5=average
Our goal for the average is 90
(79+94+91+92+test5)/5=90
79+94+91+92+test5=90*5
test5=450-79-94-91-92
Test5=94