1.8x-3.5×0.2=2.9
1.8x-0.7=2.9
1.8x=0.7+2.9
1.8x=3.6
x=3.6/1.8
x=2
7（x+1.3）=56
x+1.3=56/7
x+1.3=8
x=8-1.3
x=6.7
（x-6）÷1.5=5
x-6=1.5×5
x-6=7.5
x=6+7.5
x=13.5