Answer:
x=4
Explanation:
-5(4-x)=-5x+20
We simplify the equation to the form, which is simple to understand 
-5(4-x)=-5x+20
Reorder the terms in parentheses
+(-20+5x)=-5x+20
Remove unnecessary parentheses
-20+5x=-5x+20
We move all terms containing x to the left and all other terms to the right. 
+5x+5x=+20+20
We simplify left and right side of the equation. 
+10x=+40
We divide both sides of the equation by 10 to get x. 
x=4