a)

$1,5x=33,5\mid :1,5$   

$x=33,5:1,5$  

$x=335:15=\frac{335}{15}=\frac{67}{3}=22\frac{1}{3}$  

 

b)

$x-20\%x=3\frac{1}{5}$  

 

$x-0,2x=3,2$  

$0,8x=3,2\mid :0,8$  

$x=4$         

 

c)

$2x+1=8\mid -1$  

$2x=7\mid :2$  

$x=3,5$  

 

d)

$\left(x+4\right)\cdot 5=80\mid :5$  

$x+4=16\mid -4$   

$x=12$