The sum of the quotient of a number and 3 and 8 is 16. What is the number?
The number is
The biggest confusion is the fact that there are two 'ands'.
There are two operations which are indicated by the words 'sum' and 'quotient'.
You need to read carefully to decide what values are being added (sum) and which are being divided (quotient).
The main sentence reads as:
The sum of something and
Using commas in the sentence will make this clearer:
The sum of, (the quotient of a number and 3), AND 8 is 16.
The quotient of a number and 3 is written as
So we have: