seven times a number minus four times the same number

Question

expression using x as a variable

simplified expression using x as a variable

Answer 1

Hi, Charles. 

To write this in math terms, we use a variable to represent the unknown number. We most often use n or x as the variable, but you can choose almost any letter. 

There are a lot of ways to write multiplication too. The most common way of writing 7 times n is simply 7n. 

So seven times a number  minus  four times the same number would be written as

7n - 4n

Because these terms have the same variable, they are called "like" terms and can be added or subtracted together.

7n - 4n = 3n

Hope this helps!

Answer 2

7n-4n=3n 

Examples:

7 apples - 4 apples = 3 apples, or

If n=2, then (7 x 2) - (4 x 2) = (3 x 2), so 14 - 8 = 6

If n=8, then (7 x 8) - (4 x 8) = (3 x 8), so 56 - 32 = 24