Numbers Puzzles

15. Which number replaces the blank and completes the sequence?
  What is the next number?
Answer
3
Working in columns, subtract the middle number from the top number and multiply by 3 to give the bottom value.
16. Which number should be written in the empty circle?
  What is the next number?
Answer
2
The numbers in each line of 3 circles, going through the centre, add up to 15.
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