You can 
put this solution on YOUR website! .
Let X be Xavier age and Y be Yolanda age (thanks for giving them appropriate names (!) )
Then
    Y + X = 126
    Y - X =   4
Add equations. You will find  Y = 
 = 65.
So, Yolanda is 65 years old now.
40 years ago, when they were married, Yolanda was 65-40 = 25 years old.    ANSWER
Solved.
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Nice problem --- thanks for posting it (!)