Represent the statement "Seven times $2$ more than a number is $21$" as a mathematical equation.

Represent the statement "The sum of three times a number and $11$ is equal to $14$"  as mathematical equation.

Write the equation represented by the following statement and state if it is a linear equation.

The product of a number minus five, and the number is sixteen.

Write an appropriate statement for the equation $2y-12=24$.

Represent the following scenario in the form of an equation.

The length of a rectangle is $1$ unit less than twice a number. Its width is $2$ units more than the same number. The perimeter of the rectangle is $32$ units.

Represent the following scenario in the form of an equation.

The number of boys in the class is $12$. The total number of students in the class is twice the number of boys plus $7$. Take the number of girls in the class as $g$.

Solve the equation $x-8=17$ using the trial and error method.