All you need to do is use the formula which is A = b x h. So, to solve, you just need to multiply 9 by 31 and I think that equals x. I'm not going to give you the answer because I want to see if you can solve it out yourself.
Update: I think I did the formula wrong. I think it's the user above who put the correct formula. Yeah, so I think you just add 9 and 31.
Anyways, just add 9 and 31 to get your answer.
