Final answer:
Ricky would need to mow 17 backyards in order to earn $306.
Step-by-step explanation:
To find the number of backyards Ricky would need to mow in order to earn $306, we can use the equation m(x) = 18x, where m(x) represents the total amount of money made when Ricky mows x backyards.
To solve for x, we can set up the equation 18x = 306.
Dividing both sides of the equation by 18, we get x = 17. Therefore, Ricky would need to mow 17 backyards in order to earn $306.