Let x = number of men
y = number of women
Then
y/(x+y) = 1/4 and after the 56 women joined the relationship is
(y+56)/(x+ (y+56)) = 5/6
The first condition gives x = 3y Substituting into the second equation gives
20y + 280 = 6y + 336 or 14y = 56 or y = 4 (number of women)
So, the number of men is x = 3y = 3(4) = 12