math student

The weight of the base only of the Statue of Liberty. Been looking in a lot of websites but no success

In a survey of 150 students, 90 were taking algebra, and 30 taking biology. a. what is the least number of students who could have been taking both classes? b. what is the greatest number of students who could be taking both courses? c. what is the greate...

4 arctan(1/3)+4 arctan(1/4)+4 arctan(2/9)=pi how do i prove it but without using this formula arctan(x)+arctan(y) = arctan( x+y/1+xy)