To solve the problem, we need to set up a system of equations based on the information provided.
Let's denote the cost of an adult ticket as \( A \) and the cost of a child ticket as \( C \). According to the problem, we have two key pieces of information:
- The total cost for 3 adult tickets and 3 child tickets is $75.
- The cost of each child ticket is $3 less than the cost of an adult ticket: \( C = A - 3 \).
From the first piece of information, we can express the total cost in an equation: \[ 3A + 3C = 75 \]
Substituting the second equation into the first gives us: \[ 3A + 3(A - 3) = 75 \]
This equation simplifies to: \[ 3A + 3A - 9 = 75 \] or \[ 6A - 9 = 75 \]
Now, to find \( A \) (the cost of one adult ticket), we will first isolate \( A \) by adding 9 to both sides: \[ 6A = 84 \]
Next, we divide by 6: \[ A = 14 \]
To find the cost of one child ticket \( C \): \[ C = A - 3 = 14 - 3 = 11 \]
Now, returning to your question about the first step, we need to solve for the total relating to both adult and child tickets.
So, the first step if solving this problem arithmetically to find the cost of one adult and one child ticket does not match any of the provided options correctly. However, the closest intention behind these options seems to be relating to rearranging the total costs.
The correct action to take would be \( 3A + 3(A - 3) = 75 \) and simplifying it, which unfortunately is not explicitly listed.
From the mechanical arithmetic steps given:
- The option to "Divide 75 by 3" is most aligned with simplifying the total cost, but it doesn't directly lead to determining individual ticket costs.
If forced to choose from the provided responses, "Divide 75 by 3" could fit as it relates to simplifying & beginning to derive an individual cost, yet preference would ideally be for a step directly incorporating the relationship of adult and child costs.