Volunteers at the park will plant 150 marigold plants and 60 petunia plants. they will plant 5 rows of petunias and twice as many rows of marigolds

The roblem is looking for how many rows of marigolds are planted. so what you need to do is writing the following equation:

M=2x5

Where m is the number of rows of marigold and 2x is two times of marigolds. When you multyply you can see that

M = 10

10 rows of marigolds are planted at the end