Robert is 15 years older than his brother Peter. However, y years ago Robert was twice as old as Peter. If Peter is now b years old and b y, find the value of b - y.

Question

Robert is 15 years older than his brother Peter. However, y years ago Robert was twice as old as Peter. If Peter is now b years old and b > y, find the value of b - y.

zpupster · Answer

P+15=R
2P     =R when we subtract the first equation from the second

2P          =R 
-P+ - 15= -R

P-15=0 add 15 both sides
P=15

at y years Robert was 30 and Peter was 15  which fits

here i am not sure what the question is asking
Peter is b meaning older than when he was at y which was 15

so anything older than 15 fits 
b-y

i guess anything >0