3分之2x÷4分之1=12
3分之2x=12*1/4
2/3*x=3
x=3*3/2
x=9/2
0.5x+5分之2x=80％—0.08
0.5x+0.4x=0.8-0.08
0.9x=0.72
x=0.72÷0.9
x=0.8