5/9 + 1/3 = 5/9 + 3/9 = 8/9 <==
Y = 3 because in a rectangle, the diagonals are ALWAYS congruent. so you would have:
5y - 2 = 4y + 1
-4y+2 -4y + 2
y = 3
You require the Pythagorean Theorem: in a right triangle, the sum of the squares of the legs equals the square of the hypotenuse.In this case 6^2 + 8^2 = 36 + 64 = 100 = 10^2
the hypotenuse is 10.