1)х + (4/15 + 7/15) = 1
x + 11/15 = 1
x = 1 -11/15
x = 1/1 - 11/15
x = 4/15
2) 1 - y = 16/21 - 8/21
1 - y = 8/21
-y = -13/21
y = 13/21
3)15 - y = 1 -21/29
15-y-1 = -21/29
14-y=-21/29
14 + 21/29 = y
14/1 + 21/29 = y
116/29 + 21/29 = y
137/29 = y
y = 4 21/29