in an experiment to measure the acceleration g due to gravity, two values, 9.96 m/s^2 and 9.72m/s^2, are determined. Find (1) the percent difference of the measurements, (2) the percent error of each measurement, and (3) the percent error of their mean. (accepted value: g= 9.80 m/s^2).

Percent difference?
Percent error of E1
Percent error of E2
Percent error of mean

How can you be to the point in your academic career where you're taking a physics class, yet you don't know how to calculate a percent?

Percent\;error = 100 \times \frac{\|measured\;value - accepted\;value\|}{accepted \; value}

I assume you know how to compute an average?