work out size of angle marked Y

Answer:
56 degrees
Step-by-step explanation:
a straight line is 180 degrees and the angle given is 124 degrees. you just want to subtract 124 from 180
180-124=56
Answer:
y = 56°
Step-by-step explanation:
y and 124 are adjacent angles and supplementary, sum to 180° , then
y + 124° = 180° ( subtract 124° from both sides )
y = 56°