Can anyone solve the following simultaneous equations?

A+B+C=360 degrees....................(1)
k^2=40^2+50^2-2(40)(50)cos(A)........(2)
k^2=30^2+50^2-2(30)(50)cos(B)........(3)
k^2=30^2+40^2-2(30)(40)cos(C)........(2)