You can put this solution on YOUR website!
Since you didnt specify what the question was, I assume that you meant to find their ages. You could let mary be represented as x and joseph be represented as y. So you could set up two equations and substitute:
You substitute equation 1 into 2. you get
To find Mary's age, you could plug in your answer for Joseph into the first equation.
So your answer would be:
Mary= 21.75 or 21 3/4 yrs old
Joseph= 7.25 or 7 1/4 yrs old