And explain how you got the answer.

Diagonals of a rectangle are equal.
AC = BD
2(x - 3) = x + 5 Remove the brackets.
2x - 6 = x + 5 Add 6 to both sides.
2x = x + 5 + 6
2x = x + 11 Subtract x from both sides.
2x - x = 11
x = 11

AC = 2 (11 - 3) = 2*(8) = 16 <<<< Answer
BD = x + 5 = 11 + 5 = 16 <<<< Answer

You have to find the angle i don’t know if i i try