Question 953159
R=Robert's age; M=Mary's age=R+2yrs
R+M=28yrs Substitute for M
R+R+2yrs=28yrs Subtract 2 yrs for each side.
2R=26yrs Divide each side by 2.
R=13 yrs ANSWER 1: Robert is 13 years old.
M=R+2yrs=13yrs+2yrs=15yrs  ANSWER 2: Mary is 15 years old.