The sum of twice a number and 5 is 9. What is the number?

Use the following relationship to set up an equation:

[ twice the number ] + 5 = 9

Step 1
Let x represent the number.

Step 2
Write an algebraic expression for "twice the number" in terms of x.
twice the number is 2x.

Step 3
Use the relationship to set up an equation.
2x + 5 = 9

Step 4
Solve the equation for x.
2x + 5 = 9
2x = 4
x = 2

So the number is 2.