the sum of 6 and 7, plus 5 times a number, is -12

the sum of 6 and 7, plus 5 times a number, is -12

The sum of 6 and 7 means we add the two numbers:
6 + 7
This evaluates to 13

Next, we take 5 times a number. The phrase a number means an arbitrary variable, let's call it x. So we multiply x by 5:
5x

The first two words say the sum, so we add 13 and 5x
13 + 5x

The word is means an equation, so we set 13 + 5x equal to -12
13 + 5x = -12 <-- This is our algebraic expression

If the problem asks you to take it a step further and solve for x, then you type this algebraic expression into our search engine and you get:
x = -5