WAEC - Mathematics (2014 - No. 44)

x^o + z^o = 180^o (sum of < on str. line)

45^o + z^o = 180^o

z^o = 180^o - 45^o

z = 135^o

z + y^o + 20^o = 180^o (sum of < s in \(\bigtriangleup\))

135^o + y^o + 20^o = 180^o

y^o + 155^o = 180^o

y^o + 180^o - 155^o

y^o = 25^o