this is how you do it: since the denomanators always stays the same you have to just change the numarator. 3x1=3, 3x2=6, 3x3=9, 3x4=12, 3x5=15, 3x6= 18, 3x7=21,3x8=24, 3x9=27, 3x10= 30 so the baker will need 30/8 cups of suger or 3 6/8 cups of suger.