Tìm x, biết: a) x = 7/25 + -1/5; b) x = 5/11 + 4/-9

a) x = 7/25 + -1/5
b) x = 5/11 + 4/-9
c) 5/9 + x/-1 = -1/3
d) 3/4 - x = 1