Note that a percentile tells us how many percents of numbers that are above the number at the percentile. So the 70th percentile tells us that 70% of the students are taller than Jake. That means 30% of the students are either at the same height or shorter than Jake.
30% of 1100 would be 0.3*1100 = 330.
So there are 330 students that are either at the same height or shorter than Jake.
