algebra
posted by Gloria .
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(D13) = B13
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.