Question

Three trolleys, A with a mass of 10 kg, B of 20 kg and C of 4 kg, are connected to each other on the surface of a table. These trolleys are then connected to a hanging block D with a mass of 6 kg as indicated in the accompanying diagram. Consider the surface of the table as well as the pulley as frictionless. 

Answer 1

$$(m_a+m_b+m_c+m_d)a=m_dg\\ (10+20+4+6)a=6(9.8)\\a=1.47\frac{m}{s^2}$$