Answer:
Go ahead and plug in the percentages and time to find the answer.
Step-by-step explanation:
The amount of a substance with half-life h, that remains after time t is 0.5t/h
Since 26% has decomposed, 74% remains.
So .74 = 0.580/h
ln .74 = (80/h) ln 0.5
h/80 = ln 0.5 / ln .74
h = 80 ln 0.5 / ln .74
h = 184.16 minutes