15x/2=60
x=60×2÷15
x=8
2.8x/2=7
x=7×2÷2.8
x=5
x-0.7x=0.51
(1-0.7)x=0051
0.3x=0.51
x=0.51÷0.3
x=1.7
10.5*7.5x=0.9
7.5x=0.9÷10.5=3/35
x=3/35÷7.5
x=175分之2