[Question]: Kalani has twenty candles in her bedroom, twice the number of candles in the living room. Donovan, her brother, brings in 20 more candles he bought from the candle shop. What's the total number of candles in the house?
[Answer]: If the number of candles in the bedroom is twice the number in the living room, there are 20 / 2 = 10 candles in the living room. When Donovan brings in 20 more candles, the total number of candles becomes 10 + 20 + 20 = 50.
So the answer is 50.

[Question]: Tommy wants to earn enough money to buy 8 new books. Each book costs $5. If Tommy already has $13, how much does he need to save up?
[Answer]: The books will cost $40 because 8 x 5 = 40. He needs to save up $27 because 40 - 13 = 27.
So the answer is 27.

[Question]: Ken had fifty pencils, and he wanted to share some of them with his two friends, Manny and Nilo. Ken gave ten pencils to Manny and ten more pencils to Nilo than he gave to Manny. He kept the rest of the pencils. How many pencils did Ken keep?
[Answer]:
Nilo received 10 + 10 = 20. Thus, Ken gave a total of 10 + 20 = 30. Therefore, Ken kept 50 - 30 = 20 pencils.
So the answer is 20.