Easy. its d, because if u put -7 and {[\72283], it will obviously exclude the factor of 12%[{9293}].
Answer: C
Step-by-step explanation:l
Answer: Medication in Lexi's system on day t becomes,

Step-by-step explanation:
Since we have given that
Initial amount Sofia takes of a medicine = 10 mg
Concentration in blood decreases by a factor of one half every day.
So, it becomes,

According to question, four days later, it becomes,

We have given that Lexi takes 10 mg of the same medicine.
So, it becomes,

Hence, Medication in Lexi's system on day t becomes,

Answer:
430
3x50 is 150 plus 280= 430
Your answer is 10^(- 4).
Think about how exponents with a base 10 work. 10^1 = 10, 10^2 = 100, 10^3 = 1000. It's just add a zero to the right side as you go up.
Then think about 10^0. Anything to a zero power is 1. Only way to go is into negative exponents now. If for positive exponents on 10 we add a zero to the right side, then for negative exponents we add them to the left. Only difference is we have a decimal.
10^(- 1) = 0.1
10^(- 2) = 0.01
10^(- 3) = 0.001
And then your answer
10^(- 4) = 0.0001
Hopefully that explanation makes sense. Exponents can be rough to explain when you're not face-to-face or using some sort of live animation to talk through it. If you're still confused, I'd suggest talking to your instructor.