Tips to study difficult subjects

The diagram represents the number of students studying different subjects. What is the number of students who study History and Biology?

Assertion: lt is very difficult to subject vinyl chloride to nucleophilic substitution as compared to ethyl chloride Reason :The vinyl group is electron donating in viny chloride

In a survey of xavirs's school of Bhubaneswar of 200 students, It was found that 120 study math, 90 study physics, 70 study shemistry, 40 study math and physics, 30 study physics and chemistry, 50 study chemistry and math and 20 study none of these subjects then the number of students study all the subjects is :

In a University there are 1200 students studying four different subjects, Mathematics, Statistics, Physics and Chemistry. 20% of the total number of students are studying Mathematics, one-fourth of the total number of students are studying Physics, 320 students are studying Statistics and remaining students are studying Chemistry. Three-fifth of the total number of students studying Chemistry are girls. 150 boys are studying Mathematics. 60% of students studying Physics are boys. 250 girls are studying Statistics. What is the total number of boys studying Statistics and Physics ?

In the given figure, how many people study only 2 subjects?

In the given figure, circles represent students studying three different subjects. How many students study all the three subjects ?