we know that
Supplementary angles are those angles whose sum is equal to \(180\) degrees
In this problem
\(x+y=180\) --------> equation \(1\)
\(x=3y\) --------> equation \(2\)
Substitute the equation \(2\) in equation \(1\)
\([3y]+y=180\)
\(4y=180\)
\(y=45\)°
Find the value of x
\(x=3*45\)
\(x=135\)°
therefore
the answer is
The measure of angle x is \(135\)°
