Answer:
x = 20
Step-by-step explanation:
I don't see a y in the diagram.
The 3 angles x, 90 and (4x - 10) lie on the line EF and sum to 180°, so
x + 90 + 4x - 10 = 180, that is
5x + 80 = 180 ( subtract 80 from both sides )
5x = 100 ( divide both sides by 5 )
x = 20
