To solve this equation, we need to first simplify the left side by using the property of logarithms that states 10^lg(x) = x:

5 * 10^lg(x) = 5x

Now we can rewrite the equation as:

5x = 7x - 15

Next, we can move 7x to the left side by subtracting 7x from both sides:

5x - 7x = -15

-2x = -15

To solve for x, divide both sides by -2:

x = 15/2

Therefore, x = 7.5.