x÷7+3×0.9=4
x/7+2.7=4
x/7=4-2.7
x/7=1.3
x=1.3×7
x=9.1
3（0.72-x+1）=4.8
0.72-x+1=4.8/3
1.72-x=1.6
x=1.72-1.6
x=0.12