Having problems with the following question.

For the equations y=sqrt{9-x} and y=x+3

a)Find the value of x when they intersect

b)Find the area between the curves from x=-1 to x=2.

-I found a to be x=0, but i am getting b wrong, weather its my arithmetic or my steps are wrong, i don't know.

-When inputting the two functions into an integral equation, should i take them away? multiply them? or......... i have been taking them away.

If anyone could help me with this, it would be greatly appreciated, thanks.