Answer:
he will have to go one more week and all together it would be five weeks
Step-by-step explanation:
16/4=4
you need four more to get to 20, and if he does 4 quizzes a week he only needs one more week.
6x+3y=15
6*2+3y=15
12+3y=15
3y=3
y=1
6x+3y=15
6*5+3y=15
30+3y=15
3y=-15
y=-5
The answers is y=1 & -5