make the mixed number improper ( multiply whole number by denomentaor then add that number to the numerator and put it over the orignial denominator) to get this
(15/2)/(21/4)=x/9
we know that a/b/c/d = a/d * d/c
so 15/2*4/21=60/42=x/9
simplify
30/21=x/9
10/7=x/9
10/9*9/1 (10/9*9) =x
90/9=x
10=x
