OK. Take a look at the number just to the right of the digit you want to round to. Since your number is 2,874,992 the digit in the 10,000th place is 7. The digit just to the right of that digit is 4. Now ask yourself... Is that digit less than 5? If it is, then replace that digit and all the other digits to the right with 0, so you get 2,870,000 as the properly rounded result.
Now let's make a minor change to show rounding up. If you were given the number 2,875,992 then instead of a 4, you would have 5 as the digit just to the right of the 7. And the answer to the question "Is that digit less than 5?" would be no. In which case you still replace that digit and all the others to the right with 0, but you'll also add 1 to the digit you're rounding, getting 2,880,000
But for this problem, the properly rounded result is 2,870,000
Unlike the other variables, 4y has a y instead of an x. The numbers with an x variable can all be combined, but 4y can't be combined with an x variable.
