ricee

thanks for help 

$\frac{24x^2y}{8xy} = 3x$

3.) 105 = 1*3*5*7

3 digit number : 3, 5, 7. total permutations : 3! = 6

4 digit number : 1, 3, 5, 7. total permutations : 4! = 24

total : 6 + 24 = 30

$310 \equiv 37 \pmod {K}$

$310-37 \equiv 273 \equiv 0 \pmod K$

Factor of 273 : 1, 3, 7, 13, 21, 39, 91, 273

Largest possible two-digit positive integer K is 91