Question

What are the values of x and y?

Answer 1

x + 123 = 180 (angle on a straight line)

subtract 123 from both-side of the equation

x + 123 - 123 = 180 -123

x=57

x + y = 180 (angle on a straight line)

57 + y = 180

subtract 57 from both-side of the equation

57 - 57 + y = 180 -57

y = 123