(13-x):3 = 2
13-x = 2*3
13-x = 6
-x = 6-13
-x = -7
x = 7
[tex]\it (13-x):3=2\Rightarrow\dfrac{13-x}{3}=2\Rightarrow13-x=3\cdot2\Rightarrow13-x=6\Rightarrow x=7[/tex]