how many cards can be cut from 24 3/4 inches wide stock if each card is 1 3/8 inches wide?

99/4 / 11/8
= 8 x 99 / 4 x 11
= 792 / 44
= 18

Just divide:
24 3/4 ÷ 1 3/8

But first convert those mixed numbers to improper fractions:
99/4 ÷ 11/8

Then switch the division to a multiplication by the reciprocal:
99/4 x 8/11

You can do some canceling:
9/1 x 2/1
= 18/1
= 18

Answer:
18 cards

24 3/4 / 1 3/8

=24.75/1.375

=18 cards