Sofia takes 10mg of a medicine whose concentration in blood decreases by a factor of one half every day. Let t be the number of days since Sofia took the medication. The amount of medication in her system after t days is S = 10(½)t. Four days later, Lexi takes 10mg of the same medicine. How much medication, L, is in Lexi’s system on day t?

L = 10(1/2)t

L = 10(1/2)t + 4
L = 10(1/2)t – 4

L = 10(1/2)4t

Which equation below compares the amount of medicine, S, in Sofia’s system with the amount of medicine, L, in Lexi’s system?

L = 16 x S

S = 16 x L

L = 4 + S

S = 4 + L