Common denominator : The common denominator of two or more fractions is a number that is a multiple of all the denominators of the fractions. For example 12 and 24 are both common denominators of $\frac{3}{4}$ and $\frac{1}{6}.$

Denominator : The denominator of a fraction $\frac{a}{b}$ is the number $b$ below the fraction bar.

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.

Least common denominator : The least common denominator of two fractions is the least common multiple of the two denominators of the two fractions. For example the least common denominator of $\frac{3}{4}$ and $\frac{5}{6}$ is 12.

Multiplication : Multiplication is the mathematical operation that is a shorthand for adding the same amount several times. For example $3\cdot 4=4+4+4=12.$

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

One ninth : One ninth is the number $\frac{1}{9}=0.\overline{1}.$

Third : A third either refers to the third object in an ordering or to the number $\frac{1}{3}=0.\overline{3}.$