Answer: The size of angle x in a regular pentagon is 72 degrees.
To find the size of angle x in a regular pentagon, you need to divide the total number of degrees in a full circle (360) by the number of sides in a pentagon (5).
A full circle has 360 degrees, so each interior angle of a regular pentagon must measure 360/5 = 72 degrees.
Therefore, he size of angle x in a regular pentagon is 72 degrees.