Variable and constants

Q. There are three consecutive numbers whose sum is 129. Find the square of the middle one.

1. 1849
2. 1764
3. 1829
4. 1936

Q. If $\frac{x}{pq}+\frac{x}{qr}+\frac{x}{pr}=p+q+r$, then find the value of$x$.

1. $pqr$
2. $\frac{p}{qr}$
3. $\frac{q}{pr}$
4. $\frac{pq}{r}$

Q. How many variables are there in the expression (xy + 5)?

1. 0
2. 1
3. 2
4. 3

Q. Help John solve this mathematical puzzle:

The difference between two numbers is 1. If so, what will the difference between their squares be?

1. Same as the sum of the numbers
2. 1
3. Same as the product of the numbers
4. Cannot be determined

Q. If $\frac{x+c}{x+1}=c+1$. Express $x$ in terms of $c$.
Given c is a constant, $c\ne 0$, $c\ne -1$ and $x\ne -1$.

1. $\frac{-1}{c}$
2. $c-2$
3. $\frac{c-1}{c}$
4. $\frac{c-1}{c+1}$