Find angle x in the following figure:

We know that, 

In isosceles triangle, the two angles opposite to the two equal sides are equal.

By angle sum property of a triangle,

$x+{45}^{°}+{45}^{°}={180}^{°}$

$x+{90}^{°}={180}^{°}$

$x={180}^{°}-{90}^{°}$

$x={90}^{°}$