Final answer:
Without the value of 'x', we cannot determine the exact measure of angle RST. If provided with 'x', we could substitute it into the expression (6x + 12)° to find the measure.
Step-by-step explanation:
To determine the measure of angle RST represented by the expression (6x + 12)°, we need to know the value of 'x'. Unfortunately, the question does not provide a specific value for 'x', and without this information, we cannot calculate an exact measure for angle RST. Instead, we can say that the measure of angle RST in degrees is dependent on the value of 'x'.
If provided with the value of x, you could substitute it into the expression and simplify to find the angle's measure. For example, if x equals 10, then the measure of angle RST would be 6(10) + 12 degrees which equals 60 + 12 degrees, resulting in a measure of 72 degrees for angle RST.
Since the specific value of 'x' is not given in the question, we can't select an answer from the provided choices A. 78°, B. 84°, C. 120°, or D. 156°. Each of those values would require a specific corresponding value for 'x'.