Since the angles are supplementary, their measures add up to 180 degrees.
You have:
- \( m∠QRS = (x + 30)° \)
- \( m∠SRT = (2x)° \)
Setting up the equation:
\[ (x + 30) + (2x) = 180 \]
Combining like terms:
\[ 3x + 30 = 180 \]
Subtracting 30 from both sides:
\[ 3x = 150 \]
Dividing by 3:
\[ x = 50 \]
Now substitute \( x \) back into the expression for \( m∠QRS \):
\[ m∠QRS = (50 + 30)° = 80° \]
Thus, the value of \( m∠QRS \) is \( \boxed{80} \) degrees.