You can put this solution on YOUR website! Don is 3 more than the age of tom,
d = t + 3
or
t = d - 3
:
and in 9 yrs he will be 3 times as old as tom was 4 years ago.
d + 9 = 3(t-4)
d + 9 = 3t - 12
d = 3t - 12 - 9
d = 3t - 21
replace t with (d-3)
d = 3(d-3) - 21
d = 3d - 9 - 21
d = 3d - 30
30 = 3d - d
30 = 2d
d = 30/2
d = 15 yrs is Don's age
:
:
See if that checks out in the statement (Tom is 12 yrs old
"In 9 yrs he will be 3 times as old as tom was 4 years ago."
15 + 9 = 3(12 - 4)
24 = 3(8)
