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

.
Answer:
the answer is the last one, you solve this by comparing the lines from each shape. these shapes are congruent, meaning they're the same, so the like AB on the first shape and EF on the second are the same, and so on if that makes any sense. surely someone else could do a better explanation than me tho
An equilateral triangle is a triangle where all sides are of equal lengths. So, the angles are of equal values as well which is 60. We use the angle and the height of the triangle to determine the side length. We do as follows:
tan (60) = 15 / base/2
base = 10√3 = side length