During an isothermal expansion, a confined ideal gas does 150 J of work against its surroundings. This implies that 

If a process is expansion then work done is positive 

$$\begin{gathered} \mathrm{Q}=△\mathrm{U}+\mathrm{W} \\ \Rightarrow \mathrm{Q}=\mathrm{W} (\mathrm{For} \mathrm{isothermal} \mathrm{process}, △\mathrm{U}=0) \end{gathered}$$

As per question work done by gas is given as 150 J so same amount of heat is absorbed by gas.