Write the sentence below as an equation and solve for the number. Let the variable $x$x represent the number.

"If $11$11 is subtracted from a number, the result is $-7$−7."

Write the sentence below as an equation and solve for the number. Let the variable $y$y represent the number.

"The quotient of a number and $-3$−3 is $-20$−20."

Vanessa is cutting out a rectangular board to construct a bookshelf.

The board is to have a perimeter of $48$48 inches, and its length is to be $3$3 inches shorter than double the width.

When a number is added to both the numerator and denominator of $\frac{1}{5}$15, the result is $\frac{3}{7}$37.

Form and solve linear and simple quadratic equations