Sam and Nick age problem

Sam is 9 years older than nick. 7 years ago he was 4 times as old as nick. How old is sam now?

x = Nick's age now
x + 9 = Sam's age now   {Sam is 9 years older than Nick} 

x - 7 = Nick's age 7 years ago
x + 2 = Sam's age 7 years ago   {subtracted 7 from age now} 

x + 2 = 4(x - 7)   {seven years ago, Sam was four times Nick}
x + 2 = 4x - 28   {used distributive property}
3x = 30   {added 28 and subtracted x from each side}
x = 10   {divided each side by 3}
x + 9 = 19   {substituted 10, in for x, into x + 9} 

Sam is 19

- Algebra House