How do you use Gain Bandwidth Product to estimate bandwidth at different gains?
As @SpehroPefhany mentioned, we assume that the op amp has a constant gain-bandwidth product, GBWP. That is, \$\text{GBWP}=G \cdot B\$ for any gain G and bandwidth B. From the given information, we can determine that the GBWP for this op amp must be \$96 \frac V V \cdot 8 \text{ kHz} = 768 \text{ kHz}\$. Now that we have the constant GBWP, we can solve for the gain in the second case since we know the new bandwidth, 32 kHz: \$ G = \frac {768 \text{ kHz}} {32 \text{ kHz}} = 24 \frac V V\$.