Your question asks to make an equation with the information that was given.
In order to make an equation for your question. We would be making an equation with the formula: y = mx + b.
Formula: y = mx + b
m = change
x = amount of ice cream
b = starting value
We would need to gather the key information from the question.
Key information:
You have $30
Each ice cream cost $5
With the information above, we can make an equation for the question.
What we know is that you started with $30, so that means that 30 would be your b value (starting value).
Your equation should look like this:
y = mx + 30
Now, we know that each ice cream cost $5, but since we're paying for the ice cream, we would subtract that from our starting value. This means that our change would be -5, since we are taking away $5 each time we buy ice cream.
Your equation should look like this:
y = -5x + 30
The equation above would be the equation for your question.
We would do nothing to x but just leave it as is, since we don't know how many ice creams you're going to buy.
y = -5x + 30 should be your FINAL answer.