# What is Twice the sum of a number and 9 is equal to 7?

##### 2 Answers

The expression is written

The solution is

#### Explanation:

This means you are to choose a variable to represent the "number". I will use "x"

The sum of a number and 9 is

Twice the sum of a number and 9 would be:

Now so far, this is only called an algebraic expression because while it contains a variable, it has not be made into an equation because it is not set equal to anything.

It becomes an equation when we note it is "equal to 7". Now, we write

To solve it, you first multiply:

Now "isolate the variable" by subtracting 18 from each side:

Finally, divide each side by 2:

#### Explanation:

Let's make "the sum of a number" a variable, let's say

English >> First part of the question - "What is twice the sum of a number and 9".

Math >> We know that our unknown number is some variable

English >> Second part of the question - "Is equal to 7".

Math >> Whenever you see "is" in a word problem, that almost always means "

Now, all we have to do is piece together both parts, which leaves us with:

Open the parenthesis:

Move 18 over to the other side:

Divide both sides by two to get x:

We can test whether or not we got the correct answer by manipulating this number like the word problem asked us to.

Taking this number and adding

Multiplying this number by two should then give us