(х*3+5)/4=8       9+4*(х-2)=21                        

х*3+5=8/4          4*(х-2)=21-4

х*3+5=2              4*(х-2)=17

х*3=5-2               х-2=17*4

х*3=3                   х-2=68

х=3*3                  х=68-2

х=9                     х=66