Question

Each month for 7 months, Eve reads 3 books. How many more books does she need to read before she has read 30 books?

Answer 1

how many books has she read so far? She's been doing this for 7 months, so so far she's read:

7*3=21

how many does she still need to read?

30-21=9

so she needs to read 9 more books. With 3 books a month, this means:

9/3=3

so she needs to read 9 more books, which will take her 3 months!