Okay, so we first need to locate which number is in the ten thousand place.
Ten thousand, is this 10, 000, right? Well that number has 5 digits.
Now go back to 763,400 and starting from the right, count the first 5 digits.
You should stop at the 6.
the rest is easy! Look to the right of 6, there's a 3. Since 3 is less than 5, you will not round the 6 up to 7.
SO, you keep the 7 and the 6, but turn the rest of the numbers after 6 into 0s.
Your answer should be 760,000!
I hope I made sense, if not, I will clarify anything you did not understand!