Question

When 18 is subtracted from six times a certain number,the result is -42. what is the number?

Answer 1

Let x be the number.

Then; 

6x-18=-42 (solve for x now) 
6x=-42+18 
6x=-24 
x=-4 

Therefore, this number would be -4. 

Hope I helped :) 

Answer 2

To start off, you want to create an equation. 18 subtracted six times from a certain number (let's use a variable 'x') would look like: 6x - 18.
6x - 18 = -42

Next, isolate the variable by adding 18 to both sides.
6x - 18 = -42
    + 18   + 18
       6x = -24

Lastly, solve for x.
6x/6 = -24/6
x = -4