Oh! So, Vac = 25/65 = 0.38c and Vcb = 35/65 = 0.58c
So, plugging in:
0.38c+0.54c / 1 + (0.38c)(0.54c)/c^2
= 0.71c, so truck is traveling 49m/s relative to the car? That makes more sense, because it would seem to be traveling faster than it actually is when viewed from the car's frame. Is that...