Answer:
I get 458, but please check the calculations.
Step-by-step explanation:
See attachment. I worked down the pyramid until I has enough information to calculate x. For example, 919 had to be the difference of (1729 - 810) for a sum of 1729. 129 had to be the difference of (919-790). 681 is the difference of (810 - 129). And so on . . .
