The phrase a number means an arbitrary variable. We can pick any letter a-z except for i and e. Let's choose x. Twice a number: 2x decreased by eight 2x - 8 is means equal to. Set 2x - 8 equal to zero for our algebraic expression: 2x - 8 = 0 If the problem asks you to solve for x, add 8 to each side: 2x = 8 Divide each side by 2: x= 4
