Answer:
x=45
Explanation:
In order to solve for x, you would need to get the variable by itself. First, we would divide 1/3 on both sides. 
10 = 1/3 (x - 15)
10 / (1/3) = (x - 15)
30 = x - 15
Then we would add 15 to both sides. 
45 = x 
Then, we can check our work by plugging the value of x into the original equation.
10 = 1/3 (x - 15) 
10 = 1/3 (30)
10=10 
The correct answer is x = 45