After sharing $x$ pencils with your friend, you are still left with $7$ pencils. Express the total number of pencils before sharing.

If the cost of a table and a chair is $x$ and $y$ respectively, then find the total cost of $4$ chairs and a table.

Sanjay scored double the runs in test match $1$ than in test match $2$. If he scored one-third of the sum of the runs scored in test match $1$ and test match $2$, in test match $3$, then find his total runs in test match $3$.

Find a rule for finding the perimeter of an equilateral triangle. 

Find a rule for distributive property over subtraction and verify the same.

Find a general rule to find the perimeter of a rectangle whose length and breadth are $l$ and $b$, respectively.

The side of a regular pentagon is denoted by $l$. Find a rule for the perimeter of pentagon using $l$. 

In the figure given below, $DE$ is the diameter of a circle. So, express the diameter of the circle in terms of its radius.

The equal sides of an isosceles triangle is $a$ and that of the unequal side is $b$. Express the general rule for the perimeter of the isosceles triangle.