Numbers Puzzles

3. Place the numbers 1 - 12 in the twelve circles below so the sum of each side of the triangle is 36. I will give you a head start by placing some of the numbers for you. (The numbers may be used once only).
  What is the next number?
Answer
4 .
4. What is the missing number in the pie below?
  What is the next number?
Answer
The missing number is 6.The two numbers opposite each other always total
21 : 15 + 6 = 21.