Lines LM and LP are tangent to the circle at points M and P respectively. The dashed radius lines are perpendicular to those tangents, which means we have 90 degree angles at points M and P.
For any quadrilateral, the four angles always add to 360 degrees.
L+M+O+P = 360
L+90+165+90 = 360
L+345 = 360
L = 360-345
L = 15
Another route you can use is the fact that opposite angles L and O are supplementary
