(1)1500/x-18=1500/2.5x
1500/x-18=600/x
1500/x-600/x=18
900/x=18
18x=900
x=50
(2)12/x=36/x+8
12/x-36/x=8
12-36=8x
8x=-24
x=-3
(3)15/2x-1=15/x
15-2x=30
-2x=30-15
2x=-15
x=-7.5
(4)40/x+3=30/x-3
40/x-30/x=-3-3
10/x=-6
6x=-10
x=-5/3
(5)1280/3.2x-11=1280/x
400/x-11=1280/x
400-11x=1280
-11x=1280-400
11x=-880
x=-80