Of 300 surveyed students, 20% of those who read book A also read book B and 50% of those who read book B also read book A. If each student read at least one of the books, what is the difference between the number of students who read only book A and the number of students who read only book B?
Choose the correct choice from the following answers:
A) 120
B) 125
C) 130
D) 135
E) 150
Say the number of students who read book A is A and the number of students who read book B is B.   Given that 20% of those who read book A also read book B and 50% of those who read book B also read book A, so the number of students who read both books is 0.2A=0.5B --&gt; A=2.5B.   Since each student read at least one of the books then {total}={A}+{B}-{Both} --&gt; 300=2.5B+B-0.5B --&gt; B=100, A=2.5B=250 and {Both}=0.5B=50.   The number of students who read only book A is {A}-{Both}=250-50= 
<gadget id="calculator">250-50</gadget>
<output>200</output>
200;   The number of students who read only book B is {B}-{Both}=100-50= 
<gadget id="calculator">100-50</gadget>
<output>50</output>
50;   The difference is  200-50= 
<gadget id="calculator"> 200-50</gadget>
<output>150</output>
150.   Answer: 150.
<result>E</result>
Of 300 surveyed students, 20% of those who read book A also read book B and 50% of those who read book B also read book A. If each student read at least one of the books, what is the difference between the number of students who read only book A and the number of students who read only book B?