The other tutor has told you how to find 2 of the solutions but there are 4 solutions in all. That's because the right angle can also be at the point (5,8) or at the point (-4,11). The way he showed you will give the green and the blue solutions in the drawing below, but you'll also need to find the black and red solutions.If you need any further assistance (which you probably won't), you can ask me in the thank-you note form below, and I'll get back to you by email. Edwin