A line crossing two parallel lines creates big angles and small angles. The big angle that matches y is split by a line perpendicular to d and e. The big angle is 58+90=148, which is also the value for y. Another way to solve this is to find the third angle of the triangle: 180−90− 58=32. The 32∘ angle and the y∘ angle make up a straight line, so 180−32=148.