for 27, check the left-side of the picture below.
the arc has 88°, and therefore the central angle also has 88°.
notice the red tickmarks, since those two segments are radius, they are equal, that makes an isosceles triangle, with a "vertex" of 88°, and twin sides on the "bases".
so 180 - 88 is 92, and since "x" and the other angle are twins, 92/2 is "x".
for 29, check the right-side of the picture below.
"x" is sitting on a flat-line that runs through the center of the circle, and therefore that line is the diameter, now, a flat-line is always 180°.
we know the arc there is 130°, so, the arc of the area where "x" is at is 180° - 130°, now, that arc is the "intercepted arc" from an "inscribed angle".
by the "inscribed angle theorem" that you see there below, "x" is half that arc.
