Answer
$120^{\circ}$
Work Step by Step
Add $360^{\circ}$ as many times as needed to obtain an angle with measure greater than $0^{\circ}$ but less than $360^{\circ}$.
$-5280^{\circ}+(15\cdot360^{\circ})=120^{\circ}$
This is the angle of least positive measure that is coterminal with $-5280^{\circ}$.