Question

How to write the quotient of a number plus 6 and 3 as a variable expression

Answer 1

Quotient of means divide ... look for the word "and" to place your division sign
The sign can be ÷ or a fraction bar /.
Because x plus six come after "quotient of" but prior to the "and" they must be considered as a group so use some form of grouping symbols if not in fraction from:
(x + 6) ÷ 3 or $\frac{x+6}{3}$