Question 917711
Add some unknown number x years to both ages.  Erica will be 8+x years old.  Mom will be 42 + x.  The goal is to find x so that 3(8+x) = 42 + x - mom is three times as old.<P>
3(8+x) = 42 + x<P>
24 + 3x = 42 + x<P>
2z = 18<P>
x=9<P>
In 9 years Erica will be 17 and mom will be 51.  3 x 17 = 51