posted by Gloria on .
Betty is 6 years older than Deb. 13 years ago, Betty was 4 times older than Deb. How old is Deb?
D + 6 = B
4(D-13) = B-13
Substitute D+6 for B in second equation and solve for D. Insert that value into the first equation and solve for B. Check by inserting both values into the second equation.