turn into algebraic expression

Question

the sum of a number and 12 divided by 9

Answer 1

the exact meaning of the question is ambiguous, it could be

the sum of a number and 12, then divided by 9: (x+12)/9

or the sum of a number and another number which is 12 divided by 9: x+12/9

Answer 2

the way your problem is worded, this is what it can be: [ x + 12 ] / 9