(1/4+1/5) х = 1 4/5
(5+4)x/20 = 9/5
9x/20 = 9/5
9x = 20*9/5
9x = 4*9
x = 4*9/9
x = 4
(2 1/12 - 1 5/6) х = 3/4
(25/12 - 11/6)x = 3/4
(25 - 22)x/12 = 3/4
3x/12 = 3/4
3x = 12*3/4
3x = 9
x = 3
4/15 y = 2/5
4y/15 = 2/5
4y = 15*2/5
4y = 6
y = 1.5
7/8 y = 14
7y/8 = 14
7y = 14*8
y = 14*8/7
y = 16
9/10 y = 4 1/2
9y/10 = 9/2
9y = 9*10/2
9y = 45
y = 45/9
y = 5