The expression "a number" can be represented with any letter. Use, for instance, the letter n.
Then, the expression "The quotient of a number and 6" can be represented as:
[tex]\frac{n}{6}[/tex]9 more than the quotient of a number and 6 can be expressed as:
[tex]9+\frac{n}{6}[/tex]If that expression is equal to 3, then:
[tex]9+\frac{n}{6}=3[/tex]Which is an algebraic expression for "9 more than the quotient of a number and 6 is 3".