This is a very interesting problem! Can you recall any relation between two sides of a triangle and the angle between them?
You should remmber the Law of Cosines, which is:
c2 = a2 + b2 - 2ab cos(θ)
Does that look familiar?
Here, c is the longest side, and a and b are the shorter sides. Theta is the angle between them.
Use implicit differentiation to get...
2c (dc/dt) = -2ab(-sin(θ)) dθ/dt
You want to solve for (dc/dt) now. Remember to convert your angles from degrees to radians. 60 degrees is π/3. 2 degrees/min converts to 2*π/180 = π/90
2c *dc/dt = 2*(11)(18)*sin(π/6)*π/90
Find 'c' using the original law of cosines, then solve for dc/dt. I will leave the final steps for you to figure out.
I hope this helps!