Question

I need to solve the following equation and show all work. 2.4 + c = -40

Answer 1

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

Answer 2

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.