So hmm notice the picture below
so all internal angles then, are "a", "a", 90, 113, and 105
now the sum of all internal angles of a regular polygon, is 180( n - 2), where n = number of sides in the polygon
well, this is a PENTAgon, or PENTA=5, 5 sides, so, it has a total of
180( 5 - 2) internal angles or 540
thus
![\bf a + a + 90 + 113 + 105 = 540\implies 2a+90 + 113 + 105 = 540 \\\\\\ 2a=540-308\implies 2a=232\implies a=\cfrac{232}{2}\implies \boxed{a=116}](https://tex.z-dn.net/?f=%5Cbf%20a%20%2B%20a%20%2B%2090%20%2B%20113%20%2B%20105%20%3D%20540%5Cimplies%202a%2B90%20%2B%20113%20%2B%20105%20%3D%20540%0A%5C%5C%5C%5C%5C%5C%0A2a%3D540-308%5Cimplies%202a%3D232%5Cimplies%20a%3D%5Ccfrac%7B232%7D%7B2%7D%5Cimplies%20%5Cboxed%7Ba%3D116%7D)
since, angle "y" is sitting on a flat-line with angle "a", then, y = 180 - a
and, sure you know how much that is