Cascading op-amps

I am trying to figure out the gain of the following circuit:

What I have done so far is looking at each amplifier independently:$$U_3=-R_9/R_8=-4$$$$U_4=R_{10}+R_{11}/R_{10}=3$$$$V_o=-R_9/R_8 \times (R_{10}+R_{11}/R_{10})=-12$$And have gotten -12 as the final answer. However, the questions hints at "cascading the transfer functions". Does my method look correct? What am I doing wrong here?