42.5, just need to multiply
Answer: FIRST OPTION
Step-by-step explanation:
According the quotient of powers property, when you have the division of two powers with the same base, then you must subtract the exponents.
Therefore, keeping the property above on mind, you have that the quotient is the shown below:

7/10 because you divide by 10
If you cut it in half every two hours, the answer will be 10.9375 mg.
Https://www.desmos.com/calculator you can use this calculator just plug the what y= in it and it will show you the graph and the vertex