20-x=12.6
1.5x-3.8=5.2
13(5+x)=169
4.2-3.8=
24÷0.8=
5.6×0.5=
10.3+2.45=
8.4÷2.1=
2.5×4÷2.5×4=
5x+5=25(解方程)