Juan put three square tiles with sides 8 centimeters, 10 centimeters, and x centimeters together so that they form a right triangle. which statement is true about the area a of the smallest tile?

The smallest triangle is not going to be determined by the a plus sign between the largest square and one of the small ones. That eliminates the two top answers. 

A right triangle has the pythagorean equation associated with it.

That's a^2 + b^2 = c^2

Both the top right answer and the bottom left answer are eliminated because they are not of this form.

The largest side is c so to find x you need to subtract 8^2 from 10^2

10^2 - 8^2 is the answer <<<<<