I will start you out. Let's assign...
x=smaller number
x+9=larger number
The problem states when added, they equal 43. So...
(smaller#) + (larger#) = 43
x + (x+9) = 43
Now combine like terms and solve for "x".
Substitute back into to each number assignment above and simplify.
Comment if you need further explanation. Don't forget to check your answer!