Question

If x/4 = y/5, then x+4/4 = ?/5

Answer 1

Assuming you mean

(x+4)/4

x/4 = y/5 means x = 4 y/5
then
x+4 = 4 y/5 + 20/5 = (4y+20)/5
so
(x+4) / 4 = (y+5)/5