The sum of two complementary angles is 90°. For one pair of complementary angles, the measure of the first angle is 15 less than twice the measure of the second angle. Write a system of equations that can be used to determine the measure of the first angle, a, and the measure of the second angle, b.
•a+b=90
a-2b=15
•a+b=90
2b-15=a
•a+b=90
2b+15=a
•a+b=90
2a-15=b