We are given in the question that 3 oz. of sugar is contained in 10 oz. of cereal.
To find the amount of sugar in 25 oz. of cereal, we first calculate the amount of sugar per ounce:

Therefore, the oz. of sugar in 25 oz. of cereal is gotten by multiplying as shown below:

Therefore, there is 7.5 oz. of sugar in 25 oz. of cereal.