Explanation:
2 things to remember :
the sum of all angles in a triangle is ashtrays 180°.
the sum of all angles around a point on one side of a line is also always 180° (because that represents a half-circle).
let's call the 3rd angle in the triangle "innerQ".
so,
180 = (4x + 13) + 19 + innerQ
180 = (7x + 2) + innerQ
as innerQ is also the supplementary angle of 7x + 2.
because of that, we can now say
(4x + 13) + 19 + innerQ = (7x + 2) + innerQ
4x + 13 + 19 = 7x + 2
4x + 32 = 7x + 2
30 = 3x
x = 10
so, the angle S = 4×10 + 13 = 40 + 13 = 53°