Percentage wise, we are understanding that 100% of the population equals all 3,600 students, and that only 40% eat cold pizza for breakfast. This means that 60% do not eat cold pizza for breakfast, so:
3600 students x 0.6 (or 60/100) = 2,160 students who do not eat cold pizza for breakfast.
Rounding as accorded to the question, the answer would then be 2,200 students when rounded to the hundredths place.