Hello.
1 fl oz is equivalent to 1/8 cups, or 0.125 as a decimal. To solve for how many cups 100 fl oz is, we need to multiply both our values by 100;
1 x 100 = 100
0.125 x 100 = 12.5
Your answer is:
100 fl oz is equivalent to 12 cups and 4 fl oz.
I hope this helps!