Question 713078
 Michael is 15 years older than his brother Rafael.
 However, y years ago Michael was twice as old as Rafael.
 If Rafael is now x years old and x > y, what is the value of x-y?
:
" Michael is 15 years older than his brother Rafael." Rafael is x 
m = x + 15
:
"y years ago Michael was twice as old as Rafael."
m - y = 2(x - y)
m - y = 2x - 2y
m = 2x - 2y + y
m = 2x - y
Replace m with (x+15)
x + 15 = 2x - y
15 = 2x - x - y
15 = x - y