Three forces in a plane act on an object. The forces are 7 N, 11 N, and 15 N. The angle between the 7 N and 11 N forces is 105degrees, between the 11 N and 15 N forces is 147degrees, and between the 15 N and 7 N forces is 108degrees.

a) Are the vectors in equilibrium?

b) If not, find the magnitude and the direction of the resultant force.

I can do problems with two vectors just fine, but I'm not sure how to solve with three vectors.