Concept:The sum of the interior angles of a quadrilateral is always 360∘.Explanation:Add all the given angles and set the sum equal to 360∘:(3y+10)+(2y+30)+(y+20)+4y=360.Combine like terms:3y+2y+y+4y=10y,10+30+20=60.So the equation becomes:10y+60=360.Subtract 60 from both sides:10y=300.Divide both sides by 10:y=30.Answer:y=30∘The correct option is C.