Question 370160
The 333 who take Algebra includes both those who take Algebra and Biology and those who just take Algebra.  With 188 who take both, this means that 333-188 or 145 freshmen take just Algebra.<br>
The 306 who take Biology includes both those who take Algebra and Biology and those who just take Biology.  With 188 who take both, this means that 306-188 or 118 freshmen take just Biology.<br>
So we have 145 who just take Algebra, 118 who just take Biology and 188 who take both. This adds up to 451 freshmen. The other freshmen must take neither:
480-451 = 29 freshmen who take neither.