I read this as: (4hj^2/10j^3)(3h^3k/h^3k^3). Take the second brackets first: h^3 cancels and we're left with: 3k/k^3, which simplifies to 3/k^2. Now the first brackets: simplify the j's: 4h/10j, now the numbers, dividing by common factor 2: 2h/5j. Now we can multiply: 2h/5j*3/k^2; multiply the numerators: 6h then the denominators: 5jk^2 and rebuild the fraction: 6h/5jk^2.