Three adult and three child movie tickets were purchased for $75. The cost of each child ticket is $3 less than the cost of an adult ticket. Identify the first step if solving this problem arithmetically, which would find the cost of one adult and one child ticket. (1 point)
Let x be the cost of an adult ticket.
The cost of a child ticket is x - 3.
Three adult tickets cost 3x.
Three child tickets cost 3(x-3).
The total cost is 3x + 3(x-3) = 75
The first step is to write the equation: 3x + 3(x - 3) = 75