This question can be solved using algebra

Let number of sequins be x and beads be x since they are equal

Since the unknown right now is the number of cards decorated, we will try to find this unknown

1. Since number of cards = number of beads/number of beads used in each card

number of cards = x/5

Since 3 sequins are used for each of the same card, by using the formula in 1,

number of sequins used = x/5 * 3 = 3/5 x

Since we now know the original number of sequins, how many sequins is used and how many are left over, we can form an equation

original number of sequins = sequins used + sequins left over

x = 3/5x + 56
2/5x = 56
x = 140

So number of beads and sequins are both 140

Now after this since 7 sequins are used until all are used up, we can find the number of cards decorated again by number of sequins originally/number of sequins used per card

Number of cards = 140/7 = 20

So since 5 beads per card, total number of beads used = 20 * 5 = 100

Number of beads left = 140 -100 = 40 (answer)

Hope this helps!