Two angles are supplementary if their sum equals \(180^\circ\). Given the measures of the angles:
\[ m∠QRS = (x + 16)^\circ \] \[ m∠SRT = (3x)^\circ \]
We can set up the equation for their sum:
\[ (x + 16) + (3x) = 180 \]
Combining like terms gives:
\[ 4x + 16 = 180 \]
Next, we will isolate \(x\) by subtracting 16 from both sides:
\[ 4x = 180 - 16 \] \[ 4x = 164 \]
Now, divide by 4:
\[ x = \frac{164}{4} = 41 \]
Now that we have \(x\), we can find the measure of angle \(SRT\):
\[ m∠SRT = 3x = 3(41) = 123 \]
Thus, the measure of \(∠SRT\) is:
\[ \boxed{123^\circ} \]