Hello tomh381

Your working is perfect up to this point. Thanks for showing us what you've done so far.

All you need to do now is to make the subject of your last equation:

(1)

and substitute into your equation A to eliminate . You'll then get a quadratic equation in , which will factorise to give you two values. Substitute back into equation (1) here, and you're done.

Can you complete this now?

Grandad