Internal energy is a state function and the change in the internal energy is zero for isothermal process.

In the given information, two processes are isothermal and one process is adiabatic. Therefore, the net change in the internal energy is equal to the change in the internal energy during the adiabatic process. Therefore,

$∆U_{\mathrm{adiabatic}}=-30 \mathrm{J}$

For adiabatic process $∆Q=0$. Therefore,

$$\begin{gathered} ∆U_{\mathrm{adiabatic}}=-W_{\mathrm{adiabatic}} \\ \Rightarrow W_{\mathrm{adiabatic}}=30 \mathrm{J} \end{gathered}$$