Use the site called Desmos, it's a graphing calculator and should help you in all the ways you need. It isn't complex. Just put that equation in a box and it graphs it for you.
So first 4x12 then divide that by 7
128/8=16
3*16=48
you would need 48/8 cups of flour or simplified 6 cups
3 is to 5 as x is to 20
5 goes into 20 4 times so 3(4) gives you x
and x=12
