Question 498804
let:
x-Dave
y-ted

 the sum of the ages of Dave and ted is 48.
8 years from now ted will be 3 times Dave's age.
Find their present ages.

Equations:
x + y = 48
(y+8) = 3(x+8)

Substitute for y and solve for "x":
(x + 48-x) = 3x+24
3x = 48-24
3x = 24
x = 8 (Dave's age now)

Since x+y = 48, ted is 40 yrs old