The sum of seven and the quotient of a number xxx and eight.

Answer 1

Just translate into Math:

"The sum of seven and" ... looks like 7 + ....
"the quotient of a number xxx and eight", quotient is the result of a division, so
xxx/8

I would say : 7 + x/8
(not a good idea to use xxx as a variable, usually a single letter is used)