.
Your formulation of the given part is incorrect (which demonstrates that you do not understand what you are posting for . . . (unfortunately) )
The correct formulation of the given part is THIS:
The probability of a man to live 20 more years is X and the probability of his wife to live 20 more years is Y.
The partial answers are:
1) 1 - (1-X)*(1-Y) = X + Y - XY.
2) X*(1-Y) + Y*(1-X) = X + Y - 2*XY.
3) X*(1-Y).
------------------
This problem was posted to the forum, probably, one year ago.
See the link
https://www.algebra.com/algebra/homework/Probability-and-statistics/Probability-and-statistics.faq.question.1105633.html
https://www.algebra.com/algebra/homework/Probability-and-statistics/Probability-and-statistics.faq.question.1105633.html
and my solution there.