JAMB 2013 · UTME · Q26

If the angles of a quadrilateral are $(3y + 10)^\circ$ , $(2y + 30)^\circ$ , $(y + 20)^\circ$ and $4y^\circ$ , find the value of $y$ .

Worked solution (try it first)

The angles of a quadrilateral add up to $360^\circ$ : $(3y + 10) + (2y + 30) + (y + 20) + 4y = 360$ .
Collect terms: $10y + 60 = 360$ , so $10y = 300$ .
Divide by 10: $y = 30$ , option C.