Number : A number $x$ is a mathematical symbol representing a quantity.

Square : A square is a quadrilateral with four right angles and four equal length sides. A square is a special case of a rectangle and a special case of a rhombus.

Square root : The square root of $x$ denoted by $\sqrt{x}$ is the positive number such that $(\sqrt{x})^2=\sqrt{x}\cdot \sqrt{x}=x.$ For example $\sqrt{9}=3.$

Digit : A digit is a symbol used in the representation of a number.

Divisible : An integer $x$ is called divisible by an integer $y$ if the division $x:y$ has a remainder of zero. For example 4 is divisible by 2 but 5 is not divisible by 2.

Divisible by 3 : An integer $x$ is called divisible by 3 if $x$ is a multiple of 3. An integer is divisible by 3 if and only if the sum of its digits is divisible by 3.

Division : Division is the mathematical operation that divides objects equally into groups. More generally $x\div y$ is defined as the number that if multiplied by $y$ equals $x.$

Non-zero : Not equal to the number 0.

Number : A number $x$ is a mathematical symbol representing a quantity.

Remainder : In the division of a whole number $x$ by a natural number $y$ the remainder is the unique whole number $r$ with $0\leq r\lt y$ with $x=m\cdot y+r$ for some whole number $m.$ The remainder is the number of leftover wholes in the division. For example the remainder of the division of 14 by 3 is 2 as $14=4\cdot 3+2.$ Remainders are fundamental for the concept of congruence modulo $y$ in number theory.

Sum : A sum is the result of an addition.

Area : The amount of unit squares that is needed to cover a 2-dimensional shape.

Inch : An inch or $in$ is a unit of measurement for length. 12 inches are one foot and 1 inch is about 2.54 $cm.$

Length : Length is the attribute of a one-dimensional shape that can be measured with a measuring tape.

Product : A product is the result of a multiplication.

Rectangle : A rectangle is a quadrilateral with 4 right angles. Two opposing sides in a rectangle have the same length. They are sometimes referred to as the width and the length of the rectangle. To calculate the area of an rectangle one can multiply the width of the rectangle by the length of the rectangle. A square is the special case of a rectangle in which all side lengths are the same. Every rectangle is a parallelogram.

Square inch : Square inch is a unit of measurement for measuring area. 1 square inch is the area of a square with side length 1 inch. 144 square inches are 1 square foot.