For this case, the first thing we should do is subtract the following expressions:
2/5 of a tablespoon of cinnamon.
3/10 of a tablespoon of nutmeg.
Subtracting we have:
(2/5) - (3/10)
We apply the cross product:
((2 * 10) - (3 * 5)) / (5 * 10)
Rewriting:
((20) - (15)) / (50)
(5) / (50)
1/10
Answer:
Johnny did use 1/10 more cinnamon than nutmeg