James attached a diagonal brace across a rectangular frame that measures 6ft by 8ft what is the length of the diagonal brace

To solve this you would use the pythagorean theorem since the brace is making the frame look like two right triangles. The theorem states that for a triangle with a right angle, A^2+B^2=C^2. A and B are the sides of the frame and C is the brace which is like the hypotenuse of the triangle. It doesn't matter which side is A or B so you can put 6 or 8 in place of either in the equation. 6^2+8^2=C^2. If you simplify this it equals 36+64=C^2, which then simplifies to 100=C^2. Then you take the square root of both sides (what number multiplied by itself = the number you are trying to get, in this case, 100). So then you get C=10 because 10x10=100. So the length of the diagonal brace is 10ft.