15/3x=15/x-2/3 And 72 / 20 + x = 48 / 20-x And 1 / 2x = 1 / 4

（1）
15/3x=15/x-2/3
Multiply both sides by 3x
15=45-2x
2x=30
x=15
（2）
72/20+X=48/20-X
Multiply both sides by 20
72+20x=48-20x
40x=24
x=3/5
（3）
1/2x=1/4
Multiply both sides by 4x
x=2

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