f(3)=3(3+4)-23

Solution for f(3)=3(3+4)-23 equation:

f (3)=3 (3+4)-23

We simplify the equation to the form, which is simple to understand 
f(3)=3(3+4)-23

Simplifying terms in parentheses
f*(3)=3*(+7)-23

Reorder the terms in parentheses
+(+3f)=3*(+7)-23

Remove unnecessary parentheses
+3f=+3+*(+7+)-23

Reorder the terms in parentheses
+3f=+(+21)-23

Remove unnecessary parentheses
+3f=+21-23

We move all terms containing f to the left and all other terms to the right. 
+3f=+21-23

We simplify left and right side of the equation. 
+3f=-2

We divide both sides of the equation by 3 to get f. 
f=-0.666666666667