JAMB 1991 · UME · Q37

Angles on a straight line at the bend: the upper slanted segment makes $180^\circ - 152^\circ = 28^\circ$ with the horizontal.

Draw a horizontal line through the apex.

By alternate angles the upper segment makes $28^\circ$ with it, so the downward segment makes $28^\circ + 30^\circ = 58^\circ$ with it.

By alternate angles again, the downward segment makes $58^\circ$ with the lower line on its right-hand side.

$y$ is on the left, so $y = 180^\circ - 58^\circ = 122^\circ$, option B.