What's 9/10 of 10/7? I don't know how to divide 10/7. I know 10/7 = 1 3/10, but I cant divide it.

To solve your problem you need to multiply. 10/7 is not 1 3/10. 10/7 = 1 3/7

9/10 of 10/7 = 9/10 * 10/7

9/10 * 10/7 = 90/70 = 1 20/70 = 1 2/7