Question

If 3 subtracted from twice a number is equal to 31 more than three times the number, what is the number?

Answer 1

First, assign a variable to the unknown number:
let number = x
Now try to express in a mathematical way the information you are given about the number.:
Since
number = x
twice the number = 2x
3 is subtracted from twice the number = 2x - 3

three times the number = 3x
31 more than three times the number = 3x + 31

Since these two parts are equal, set them equal to each other:
2x - 3 = 3x + 31
Solve for x.