Hi!
When we divide a fraction for a fraction we have to multiply the first fraction for the opposite of the second (the one we're dividing for).
Let's do an example.
16/8 : 4/6 = 16/8 * 6/4
Where necessary you can do cross-semplifying.
So, 16 and 4 can be divided both for 4.
8 and 6 both for 2.
So we have 4/4*3/1
You can also semplify numerator and denominator...
4/4 = 1
1*3 = 3