Question 951309
r=Rose's age; s=Shirley's age=4r+2 years
r+12=1/2(s+12) Substitute for s.
r+12=1/2(4r+2+12) Multiply each side by 2.
2r+24=4r+14 subtract 14 from each side. 
2r+10=4r Subtract 2r from each side.
10 years=2r Divide each side by 2
5 years=r ANSWER 1: Rose is 5 years old.
s=4r+2=4(5)+2=22 years ANSWER 2: Shirley is 22 years old.
CHECK:
r+12=1/2(s+12) 
5+12=1/2(22+12)
17=1/2(34)
17=17