Which algebraic expression represents 15 less than the product of 7 and a number A. 15 - 7n

B. 7n - 15

C. 15(7n)

D. 7(n - 15)

b is 15 less thsn the product since it subtracts 15 from 7n

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)