1/u = 1/f -1/v
1/v = 1/u + 1/f
Answer:
My own answer to your question is x=10
If Jenni get one page closer to Wren every night and Wren has read 8 more pages then is will take Jenni 8 more nights to catch up to Wren. They will be on page 30 in their book.
