how tell me how you got answer 5.9 and also if you do at calculate can show me how to do pls thanks.

The steps you have are correct. I'll fill in the gap between step 2 and step 3.
[tex]0.4245 = \frac{2.5}{\text{x}}\\\\0.4245\text{x} = 2.5\\\\\text{x} = \frac{2.5}{0.4245}\\\\\text{x} = 5.8892815\\\\\text{x} = 5.9\\\\[/tex]
I multiplied both sides by x, then divided both sides by 0.4245 to isolate the variable.
With the exception of 2.5, every other decimal value mentioned is approximate.