ABC, DEF and PQRS are parallel lines. BEQ is a straight line. Angle ABE = 60° Angle QER = 80° Work out the size of the angle marked x. Give reasons for each stage of your working.

Angles ABE and EQR are alternate interior angles. This means they are the same thus angle EQR = 60˚. We know that the sum of the interior angles of a triangle is equal to 180˚ and we know that angle QER = 80˚ from the question. We can now find the value of x by subtracting -> 180˚ - 80˚ - 60˚ = 40˚.