A survey of 450 students about their subjects of interest resulted in the following outcome.

$$\bullet$$ 150 students are interested in Mathematics.

$$\bullet$$ 200 students are interested in Physics.

$$\bullet$$ 175 students are interested in Chemistry.

$$\bullet$$ 50 students are interested in Mathematics and Physics.

$$\bullet$$ 60 students are interested in Physics and Chemistry.

$$\bullet$$ 40 students are interested in Mathematics and Chemistry.

$$\bullet$$ 30 students are interested in Mathematics, Physics and Chemistry.

$$\bullet$$ Remaining students are interested in Humanities.

Based on the above information, the number of students interested in Humanities is

$$x:y:z = {1 \over 2}:{1 \over 3}:{1 \over 4}$$

What is the value of $${{x + z - y} \over y}$$ = ?

Both the numerator and the denominator of $${3 \over 4}$$ are increased by a positive $${15 \over 17}$$ integer, x, and those of _____ are decreased by the same integer. This operation results in the same value for both the fractions. What is the value of x?

Consider the following equations of straight lines :

Line L1 : 2x $$-$$ 3y = 5

Line L2 : 3x + 2y = 8

Line L3 : 4x $$-$$ 6y = 5

Line L4 : 6x $$-$$ 9y = 6

Which one of the following is the correct statement?