Carbon-11 has a half-life of about 20 minutes if we start with 200 grams how much will be left after 3 hours?

A=m(1/2)^(t/h)

a is the answer
m is the mass
h is the half-life
t is the total time

200*(1/2)^(180/20)=a
200*(1/2)^9=a
0.3906=a

Byou start by adding them all and setting them equal to 180 since that is half of the total degrees in a circle.(2x+8) + (3x-14) + (3x-14) = 1808x-20 = 1808x = 200x = 25

With a continuous thought process.