I need to solve the following equation and show all work.

2.4 + c = - 40

Well u need c to be alone so u subtract 2.4 from - 40 so c = - 42.1

It's not absolutely necessary to get rid of that decimal fraction, but you might find the solution more easily if you do this. Multiply all 3 terms by 10.

Next, subtract 24 from both sides of the resulting equation. If you've done this correctly, you'll have an equation for c, which is the answer you wanted.