What is the sum of x + 9?

So 30/48=15 / (x+9)

this could be easily solved by recognizing the proportion (the other way is usiing full algebra and doing multiply both sides by 48 (x+9) and then divide both sides by 30 then subtract 9)

30 is 2 times of 15

therefor 48 is 2 times of (x+9)

48=2 times (x+9)

divide both sides by 2

24=x+9

subtract 9

15=x

x=15