Final answer:
Doug needs 74 seed packets to grow 148 plants in his backyard, calculated using a unit rate of 2 plants per seed packet.
Step-by-step explanation:
Doug initially grew 26 plants using 13 seed packets, which means the unit rate is 2 plants per seed packet (26 plants / 13 packets = 2 plants/packet). To find out how many seed packets Doug needs to grow 148 plants, we divide the total number of plants he wants by the unit rate. So, we have 148 plants / 2 plants/packet = 74 seed packets. Therefore, Doug needs 74 seed packets to grow a total of 148 plants in his backyard.