Solve for an angle in right triangles

Right triangle lmn has vertices l(7, –3), m(7, –8), and n(10, –8). the triangle is translated on the coordinate plane so the coordinates of l’ are (–1, 8). (x, y) → (x + 6, y – 5) (x, y) → (x – 6, y + 5) (x, y) → (x + 8, y – 11) (x, y) → (x – 8, y + 11)