18.47Answer:
Step-by-step explanation:
To draw a heart, one would be choosing 1 card of 13 possible hearts, and 0 from the remaining 39 non-hearts. With respect to the entire deck, one would be choosing 1 card from 52 total cards. So the probability of drawing a heart is

When Michelle replaces the card, the deck returns the normal, so the probability of drawing any card from a given suit is the same,

. In other words, drawing a spade is independent of having drawn the heart first.
So the probability of drawing a heart, replacing it, then drawing a spade is

.
20/500
0.04 of a chance
because 1 chapter has 20 pages and the book has 500
so the chance of you flipping to chapter 12 out of 500 pages is 4% of a chance