Answer:
16 to 20 spells
Step-by-step explanation:
4 to 5 spells and you find how much you need to multiply it by and in this case it is 4. Take the 4 and multiply it to 5 and 4 and you will get your answer.
25
Luna casts 4/5 of the amount of spells that Ginny casts (busy witches), so you take 1/4 of 20 and add it to 20. In other words, add 20 + 5
