PYRAMID SCHEME:
The numbers from 0 to 9 add up to 45. If you add up the totals for the bottom three rows of the pyramid, you get 43. Therefore the number in the top block must be 2. The sum of the three shaded diagonals is 42, so 3 must be in the unshaded box. Then, for the leftmost diagonal to total 23, the two missing numbers must be 9 and 8; for the second row’s total to be 16, the missing numbers must be 9 and 7. So 9 goes between 2 and 4, next to 9 goes 7, and 8 is at bottom left. After 5 fills out the bottom row, 0 and 6 are easy to place.