Answer :
It's one of the ways to count it:
3/4 (n + 3) = 9
3/4n + 3/4 * 3 = 9
3/4n + 9/4 = 9
3/4n + 2 1/4 = 9 / - 2 1/4 (both sides)
3/4n = 6 3/4 / : 3/4 (both sides)
n = 9
3/4 (n + 3) = 9
3/4n + 3/4 * 3 = 9
3/4n + 9/4 = 9
3/4n + 2 1/4 = 9 / - 2 1/4 (both sides)
3/4n = 6 3/4 / : 3/4 (both sides)
n = 9
You will distribute the 3/4 so the equation would turn into 3/4n+9/4=9. Then you will subtract 9/4 from 9 which is 27/4. Then you divide both sides by 3/4 and the answer is 9.