Rearrange the equation by subtracting what is to the right of the equal sign from both sides of the equation :
5*(f-3)-(f+10)=0
3.1 Solve : 4f-25 = 0
Add 25 to both sides of the equation :
4f = 25
Divide both sides of the equation by 4:
f = 25/4 = 6.250