No its not
750 rounded to the nearest 100 is 800
The smallest number that would round up to the nearest 100 to make 800 is 750.
750
750
The answer depends on the units used for 750. It should be obvious to anybody that the answer for 750 microlitres will be very different to that for 750 fluid ounces, for example.
750
740
750
It is already rounded to the nearest ten.
700
750
800