Angles in Triangles Revision

Find $x$x, giving reasons for your answer.

Triangle ABC is a right-angled triangle. It is reflected about one of its edges and the two triangles together form an acute isosceles triangle. Along which edge is it reflected?

A rectangle’s length is $5$5 times its width. How many isosceles right-angled triangles can fit exactly into the rectangle if the equal side lengths of the triangle measure the same as the width of the rectangle?