HELP 7 GRADE MATH PROBLEM!!!

James is building a 10-inch by 12-inch rectangular picture frame. To assure the frame has right angles, James measures the two diagonals to see if they are equal. When the diagonals are equal, how long is each diagonal? (Express your answer to the nearest tenth of an inch.)

We know the angles are right, so we can use the pythagorean theorem in a right triangle.
Lets call the triangle ABC, with AB being the 12inch side, BC the 10inch side and AC the diagonal.
The triangle is right in B, so AC is the hypothenuse.
From the pythagorean theorem, we can say AB^2 + BC^2 = AC^2 (read the theorem if you don't understand why).
So, 12^2 + 10^2 = 144 + 100 = 244
So AC^2 = 244, and AC = root(244) = 15.6 inches at the nearest tenth.
So the diagonal is 15.6 inches at the nearest tenth.

Have you learned about Pythagorean's theorem, because it will help. So draw a rectangle with one diagonal through it. Now you see that you have two triangles. The short side of the rectangle will be 10 inches and the long side of the rectangle will be 12 inches. The slanted diagonal is what you are looking for.
Basically you find it by using this formula: x^2=10^2 + 12^2
and then you get x= sqrt(10^2 + 12^2)
and then x = 15.6 (approximately)

Yes obviously both diagonals are going to be equal anyway so it would be redundant to solve it again.

15.6 inches each
use the pythagorean theorem to solve for the missing side
10 squared + 12 squared = x squared
after solving for the missing variable the answer should come out to be about 15.6 inches
hope this helped !