ok so to solve this you need to write a proportion. start with 16/4 and set it equal to X/1. multiply across (16x1 and 4xX) and set that equal to each other (you should get 16=4X) X is the number of plants one packet grows. you next divide by 4 on both sides to get X=4, so you know one packet makes four plants. using this knowledge, you can multiply the 4 plants by 5 packets to get your answer of 20 plants.