Question

Look at the following problem and solution given by a student: Abel, Belle, and Cindy have $408 altogether. Belle has $7 more than Cindy and $5 more than Abel. How much does Abel have?

Answer 1

a+b+c=408
a=a
b=7+a
c=5+a
a+(7+a)+(5+a)=408
3a+12=408
3a=396
a=132

Abel has $132
Belle has $139
Cindy has $137

Prove:
132+139+137=408