If the cost of 20 stamps is $9.80, how
much will 1 stamp cost?

1 stamp will cost $0.49.

Step-by-step explanation:

20/9.8=1/x

cross product

20*x=9.8*1

20x=9.8

x=9.8/20

answer: the angel abc is 30°,and the abc is a triangle where the angel bac is 90°

so ac is the half of 24=12ft,and from the pythagorean theorem we find ba

ba=√bc^2-ac^2=√576-144=√432=12√3ft

so bac is 12+12√3=12(1+√3)ft