Question 950415
M=Mary=F-30; F=Father=M+30;
F=4M Substitute for M
F=4(F-30)
F=4F-120 Subtract F from each side.
0=3F-120 Add 120 to each side.
120=3F Divide each side by 3
40=F
ANSWER Mary's father was 40 when he was 4 times as old as Mary.