Hey there!
The answer to your question is x = 45
To solve this, we want to get x with a coefficient of 1 by itself on one side of the equal sign, and right now it's coefficient is 1/3. We can get a coefficient of 1 by multiplying both sides of the equation by 3.
15(3) = 1/3x(3)
45 = x
Hope this helps and if you need any further help, I would be happy to!