the sum of all interior angles in a polygon is
180(n - 2)
n = number of sides in the polygon
this polygon has 5 sides, so is a PENTAgon, so the sum of all its sides is
180(5 - 2) => 180(3) => 540
so then
[tex]\bf 90+148+(3x+10)+(x)+112=540\implies 360+4x=540 \\\\\\ 4x=180\implies x=\cfrac{180}{4}\implies x=45[/tex]
