How many eighth-size parts do you need to model 3/4? explain

To know the amount of eights you want to get something that looks like?/8. Basically, the bottom number needs multiplying by 2 (8 divided by 4 is 2). To keep the fraction accurate you multiply by 2 the top and bottom number so you get:

3/4 = (3x2) / (4x2) = 6/8