Write each phrase as an algebraic expression. Let x represent the unknown number. See Exam...

Write each phrase as an algebraic expression. Let x represent the unknown number. See Example 8.

EXAMPLE 8   Write an algebraic expression that represents each phrase. Let the variable x represent the unknown number.

a. The sum of a number and 3

b. The product of 3 and a number

c. Twice a number

d. 10 decreased by a number

e. 5 times a number, increased by 7

Solution

a. x + 3 since “sum” means to add

b. 3 · x and 3x are both ways to denote the product of 3 and x

c. 2 · x or 2x

d. 10 − x because “decreased by” means to subtract

e.

Fifteen more than a number