B = u + 2 b and u are known as variables, unknown values used as placeholders. If the variable u has the value of 10, then you plug the number 10 into the equation in the spot of the placeholder u. b = u + 2 u = 10 b = 10 + 2 Just add 10 and 2 and you have the value of b! b = 10 + 2 10 + 2 = 12 b = 12