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This number pyramid asks us to input 3 numbers, say 3, 4 and 5. It then moves up by adding 3 with 4 and 4 with 5. Finally, it will add the sum of 3 and 4 with the sum of 5. If you notice, we are adding 3 and 5 with the double of 4, so the resulting number is 16.
The number pyramid can be broken down algebraically, from which we receive:
x+y+y+z
x+y y+z
x y z
And through simplification, we receive an expression which can be used to jump from the bottom row to the row. The expression would be: 2y+x+y.