Angles x and y are supplementary. angle x is 3 times the measure of angle y. what is the measure of angle x?

45°
60°
120°
135°

So from this given deatils result that angle x and y are supplementary what mean that angle x and angle y assumed has  a measure of 180 degrees 

given that angle x is 3 time the measure of angle y 

so this mean that x=3y => 3y +y = 180 => 4y=180 => y=180/4 = 45
so angle y has a measure of 45 degrees 

x = 3y so angle x = 3*45 = 135 degrees 

the last choice is right sure 

The answer is why would a teacher ask that