Question

How do you write a variable expression for the word phrase "the sum of 9 and a number"?

Answer 1

In math, any number you don't know - and/or want to find can be named after whatever you want, but there are some conventions.

Explanation:

The most common letter used is `x`, but you won't find it strange when the variable comes as `y`, `a`, `b`, `t`... And it makes no difference!

If `x+1=2` and `y+1=2`, what's the difference? None!

In this case, you can rename it as `9+x`, using the most commonly used letter in the alphabet!