Explanation:
y + z = 180^o
z = 180^o - y
x + k = 180^o
k = 180^o - x
the sum of angles in the \(\bigtriangleup\) are: n + z + k = 180
but n + 180^o - y + 180^o - x = 180^o
n + 180^o - y - x = 0
but we want to find n
n + 180^o = x + y
but x + y = 220^o
n + 180^o = 220^o
n = 220^o - 180^o
n = 40^o