Set up a proportion:
3/4/24 = 1/x
Cross multiply:
3/4x = 24
Divide 3/4 to both sides or multiply by its reciprocal, 4/3:
x = 24 * 4/3
x = 96/3
x = 32
So you had a total of 32 muffins, now subtract this from the amount that blew away to find out how many you have left:
32 - 24 = 8
So you have 8 muffins left.