Certain number of half-lives have elapsed. a Describe this sequence.
b. Calculate how much of the substance will be left after 21 half-lives have elapsed. Show your work.
Does your answer make sense in this problem context? Why or why not?

the equivalent expression are always the hardest ones but you look at the gcf also

step-by-step explanation:

look at photo

for this case we must apply distributive property to the following expression:

the distributive property states that:

then, when applying the property we have to multiply the -2 for each term within the parenthesis:

c 5 gallons mark me as brainlest