Estimate. Then Find the sum.

740,758
-263,043
----------

700,000

-300,000
-------------
400,000

That's low, because we rounded down the minuend and rounded up the subtrahend.

400,000

To estimate the sum of 740,758 and -263,043, we can round both numbers to the nearest hundred thousand.

740,758 rounded to the nearest hundred thousand is 700,000.
-263,043 rounded to the nearest hundred thousand is -300,000.

Now, we can estimate the sum:

700,000 + (-300,000) = 400,000

To find the actual sum, we can subtract the numbers as presented:

740,758
-263,043
----------
477,715

So, the estimated sum is 400,000 and the actual sum is 477,715.