A gym teacher orders 42 tennis balls. Each package contains 3 tennis balls. Which of the following equations represents the number x of packages?
To find the amount of packages of tennis balls, take the total number of tennis balls and divide that number by the number of packages.
You didn't list the possibilities, but there is only one.
To calculate the number of packages, divide the total number of tennis balls by the number of tennis balls in each package.
Invert the fraction and multiply.