the sum of the interior angles of a polygon can be found using this formula : sum = 180(n - 2)....where n is the number of sides ur polygon has. Ur polygon has 5 sides....so the sum of ur angles are : 180(5 - 2) = 180 * 3 = 540. So ur angles have to add up to 540.
90 + 107 + 144 + 138 + x = 540
479 + x = 540
x = 540 - 479
x = 61 <===