Question

The price of oil recently went from $7.80 to $10.40 per case of 12 quarts. Find the ratio of the increase in price to the original price. (type a simplified fraction)

Answer 1

You have as a baseline, 7.80, so that's your denominator

The change is price is 7.80 - 10.40

So what they are asking is the ratio of these two quantities:
$$
\frac{7.80 - 10.40}{7.80}
$$

Answer 2

so what would be the answer