Sixteen subtracted from five times a number equals the number plus four

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The phrase a number means an arbitrary variable. We can pick any letter a-z except for i and e.

Let's choose x.

5 times a number
5x

Sixteen subtracted from five times a number
5x - 16

the number plus 4:
x + 4

Equals means we set 5x - 16 equals to x + 4 for our algebraic expression:
5x - 16 = x + 4

If you have to solve for x, type this expression into our math solver and we get:
x = 5