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For the number triangle question;

Add the bottom numbers together then times 2 to get the top number. So to find the bottom numbers by just looking at the top numbers is easy. Say the number at the top was 28. 28/2=14. 1+2+3+4=10 so that doesn't work (it needs to equal 14). 2+3+4+5=14 so there is your solution.

The possible numbers at the top goes up in eights (20, 28, 36, etc.).