Al's father is 45. He is 15 years older than twice Al's age. How old is Al? Karen is twice as old as Lori. Three years from now, the sum of their ages will be 42. How old is Karen?
Let f, a, k and l be the ages of the father, Al, Karen and Lori, respectively
f = 2a + 15
2a = f - 15 = 45 - 15
2a = 30
a = 30/2 = 15 years
Therefore Al is 15 years old
k = 2l
(k + 3) +(l + 3) = 42
k + l + 6 = 42
k + l = 42 - 6 = 36
Substituting 2l for k in above equation gives: 2l + l = 36
3l = 36
l = 12
But 2l = k
k = 2 x 12 = 24
Therefore Karen is 24 years old