)Start with the expression in parentheses and evaluate constant and each variable separately
k^2/k^4= k^-2
the square root of J^4 is j^2( I hope This is what you meant to write) and J^8/j^2= J^6 so the term in side the parentheses simplifies to (sqroot 28)(j^6k^-2) now multiply by (sqroot3)j which gives you (sqroot 84)j^7k^-2
the sqroot 84 can be further simplified to sqroot 4 x sqroot 21 which is 4sqroot21 so final answer is
(4sqroot21)j^7 k^-2
Stephen K.
01/28/21