The way to solve this problem is to isolate the X on one side of the equation.
The first step is to add 5 to both sides.
x/10 - 5 + 5 = 2/5 + 5
x/10 = 5 2/5
The next step will involve multiplying both sides by 10. First, it would be helpful to deal with the mixed number 5 2/5. You could change it to an improper fraction, but I think it's even easier to change it to a decimal: 5.4
x/10 x 10 = 5.4 x 10
x = 54