Answer:
n + 45
Explanation:
The question is asking to write an algebraic expression for the sum of a number and 45. We know we are adding a number to 45. So we use addition. But, we don't which number we are adding to 45. So we just use a variable. I used "n", but use whatever letter you want ( x, y, z, etc). I recomend using the same variable that your intrcuctor uses.
Hope this helps.