Substitution/elimination word problems

Question

Your teacher want to see if you can guess your two quiz grades. She tells you the second quiz grade is 21 points higher than the first quiz grade. She also tells you that twice the first quiz grade is 57 points more than the second quiz grade. What were your two quiz grades?

Answer 1

Quiz 1 =A

Quiz 2 = B

 

B = 21 + A

2A = 57 + B

 

2A = 57 + (21 + A)

2A = 78 + A

A = 78

 

B = 21 + A

B = 21 + 78

B = 99