Question 953256
S=Sue's age; B=bob's age=2S; M=Mary's age=S-1yr; 
B+M+S=59yrs Substitute for B and S
2S+S-1yr+S=59yrs Add 1 yr to each side.
4S=60yrs Divide each side by 4
S=15 years ANSWER 1: Sue is 15 years old.
B=2S=2(15yrs)=30 yrs ANSWER 2: Bob is 30 years old.
M=S-1 yr=15 yrds-1yr=14 years ANSWEr 3: Mary is 14 years old.
CHECK:
B+M+S=59yrs
30yrs+14yrs+15yrs=59yrs
59yrs=59yrs