Differential amplifier with two opamps
I assume Op Amps are ideal in the question. Write a KCL at the inverting input of U1 to find the output of U2 in terms of V1 and V2. Then write another KCL at the inverting input of U2. The latter will let you find an expression for the output of U1 as a function of V1 and V2. Note that due to the infinite open loop gain of the Op Amps the inverting and non-inverting inputs of each Op Amp are equal. Hope it helps.