Answer:
First, compute the z-score:
z = (x-μ)/σ = (650-500)/100 = 150/100 = 1.5
Now look up the percentile for z = 1.5 on a z-score table (http://www.z-table.com/). The percentile, p(z=1.5), is the percent of people who scored 650 or less. The percent who scored more than 650 is 1-p(z=1.5). Multiply that by the 1200 students to get the number who scored more than 650. Round to the nearest whole number (because you can't have a fraction of a person).
