The difference between a number and its two-fifth is 510. What is 10% of that number?

The difference between a number and its two-fifth is 510. What is 10% of that number?

A. 12.75
B. 85
C. 204
D. None of these
Explanation:
Let the number be x. Then,
x – 2/5 x = 510
x = (510 * 5)/3 = 850
10% of 850 = 85.