Since normality may be assumed and the mean is 500 with SD 100 then:

a)	To determine the percentile rank of a student with a score of
	350 we must determine the proportion of observations less than
	350 and so we must use the transformation rule. 
		z=(350-500)/100=-1.5
	From our tables, the proportion between -1.5 and 1.5 is 86.64%
	and so the required proportion is (100-86.64)/2=6.7%

	Hence the student is at the 7th percentile (rounded).

b)	To be at the 75th percentile the student should obtain a score
	that would result in 25% of students having a higher score. We 
	therefore need to use the transformation rule but must first,
	due to symmetry, find the z value from our table that corresponds 
	to a proportion of 50% between -z and z. The required z value is
	0.7.
		0.7=(x-500)/100
		  x=100*0.7+500=570
	Hence the student needs a score of 570 on the Math SAT.