Could someone please help me ASAP? I need a full explanation. P.S I will name u brainliest!! Thanks!

y = 90 degrees.

Step-by-step explanation: We are given that the supplementary angle of angle y is equal to 90 degrees. By definition, that means that y is also equal to 90 degrees. The solution would be:

y + 50 degrees + 40 degrees = 180 degrees

y + 90 degrees = 180 degrees

y = 180 degrees - 90 degrees

y = 90 degrees

hope this helps! :)