The easiest way to find answers for questions like these is to convert them to improper fractions, solve, and then convert them back to mixed numbers (if the question required it). When we convert these to improper fractions, we have 7/4 and 19/8. We can then find the least common denominator of the 2 so that we can solve. The least common denominator is 8, and since we are multiplying the 4 by 2 to get it there, we must also multiply the 7 by 2. Now we have 19/8-14/8. At this point, we can use simple subtraction to subtract the numerators and get 5/8.
To summarize, Cameron used 5/8 more acid in the second experiment.
