In an examination 31 student passed chemistry 29 pass physics and 3 fail both. If 50 people sat for the exam, how many of them pass chem only

This can be easily solved with a Venn diagram.

Draw a rectangle to describe the total number of people.
Inside draw 2 intersecting circles and label them C and P
Enter x in the intersection of the two circles
In the C circle enter 31-x in the "chemistry only " part
In the P circle enter 29-x in the "physics only" part
Enter 3 outside the circles but inside the rectangle, now solve
31-x + x + 29-x + 3 = 50

then evaluate 31-x

x=13

then 31-(x)13=18

To find the number of students who passed chemistry only, we need to subtract the number of students who passed both chemistry and physics from the total number of students who passed chemistry.

Given:
Total number of students who passed chemistry = 31
Total number of students who passed physics = 29
Total number of students who failed both = 3
Total number of students who sat for the exam = 50

We can use the principle of inclusion-exclusion to calculate the number of students who passed both chemistry and physics.

Number of students who passed both = Total number of students who passed chemistry + Total number of students who passed physics - Total number of students who failed both
Number of students who passed both = 31 + 29 - 3
Number of students who passed both = 57

Now, to find the number of students who passed chemistry only, we subtract the number of students who passed both from the total number of students who passed chemistry.

Number of students who passed chemistry only = Total number of students who passed chemistry - Number of students who passed both
Number of students who passed chemistry only = 31 - 57
Number of students who passed chemistry only = -26

It appears that the calculated value is negative, which suggests an error in the given information or calculations. Please double-check the information provided.