STEP 1:
Find inner angle by 123°. Let's call the inner angle x. Lines equal 180° so x plus 123° equal 180°.
x + 123°= 180
subtract 123 from both sides
x= 57°
STEP 2:
Triangles equal 180°. Add known angles and subtract from 180 to find angle y.
56° + 57° + y= 180°
113 + y= 180
subtract 113 from both sides
y= 67°
ANSWER: y=67°
Hope this helps! :)