0.5*(4.5+x)=20
4.5+x=40
x=40-4.5
x=35.5
6x-2.4*5=80
6x-12=80
6x=92
x=46/3
2分之1X-0.25X=10
0.25x=10
x=10÷0.25
x=40
x-5分之4-4=21
x-4.8=21
x=25.8
0.5*(4.5+x)=20
4.5+x=40
x=40-4.5
x=35.5
6x-2.4*5=80
6x-12=80
6x=92
x=46/3
2分之1X-0.25X=10
0.25x=10
x=10÷0.25
x=40
x-5分之4-4=21
x-4.8=21
x=25.8