The sum of x and 9 is divide by 2. That quantity is equal to 3x

Your equation would be set as 3x = (9+x) / 2 hence you proceed by putting the like terms together so x is basicly moved to the other side of the equals sign hence the equation reads 3x - x=9/2 ... after working out, you get that the result so far is 2x=4.5 ... so now simplify to find value of x, so x=2.25

(x+9) / 2=3x would be your equation set up

cross multiply to get x+9=6x

simplify to get 9=5x

divide both sides by 5 to get x alone and get 9/5 as your answer

or 1 and 4/5 or 1.8