Need with an explanation 15 points for whoever can me

Because one angle is shared between the smaller and larger triangles, this angle is clearly equal.  In addition, their sides surrounding that angle are in the same ratio, so these triangles are similar by SAS similarity, with a ratio of 2.  This means the sides of the big triangle are twice as long as the ones of the small triangle.  As a result, x is equal to 46*2=92.