1. The problem statement, all variables and given/known data Four blocks are on a horizontal surface. The blocks are connected by thin strings with tensions Tx, Ty, Tz. The masses of the blocks are A=22.0 kg, B=21.0 kg, C=17.0 kg, D=27.0 kg. Two forces, F1=83.0N and F2=50.0N act on the masses as shown. Assume that the friction between the masses and the surface is negligible and calculate the tension Tx. See attached Pic. 2. Relevant equations F = ma 3. The attempt at a solution First, I calculated the acceleration of this system. a=(F1-F2)/(mA+mB+mC+mD). a = .3793m/s^2 Then consider A and B as a whole. So F1-Tx=(mA+mB)*a Solve for Tx, which = 66.69N The correct answer is 74.7N... i really don't know what i'm doing wrong, any help / hint would be greatly appreciated. Thanks!