If 30 packets fit in 5 boxes, how many packets fit in 7 boxes?

Given that 30 packets fit in 5 boxes, we divide the total number of packets by the number of boxes.

$$\text{Packets per box} = \frac{30 \text{ packets}}{5 \text{ boxes}} = 6 \text{ packets/box}$$

Multiply the number of packets per box by the new number of boxes.

$$\text{Total packets in 7 boxes} = 6 \text{ packets/box} \times 7 \text{ boxes}$$ $$\text{Total packets in 7 boxes} = 42 \text{ packets}$$

The number of packets that can fit in 7 such boxes is $\boxed{42 \text{ packets}}$.