The sum of x and 9 divided by 2 is equal to 3x
(x + 9)/2 = 3x
Note the equal sign, what you do to one side, you do to the other. First, multiply 2 to both sides
(x + 9)/2(2) = 3x(2)
x + 9 = 6x
Subtract x from both sides
x (-x) + 9 = 6x(-x)
9 = 5x
Isolate the x. Divide 5 from both sides
9/5 = 5x/5
x = 9/5
9/5 is your answer for x
hope this helps