Question

What will the area of the wound be on day 8
On what day will the area of the Wound be less than one square millimeter

Answer 1

so hmmm if we take 70 as the first day, not the 0day
that simply means, there's another number for the 0day, when the wound happened

which means 70 is just the 70% of that number, well, 
$\bf \begin{array}{ccllll} amount&\%\\ \textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\ 70&70\\ x&100 \end{array}\implies \cfrac{70}{x}=\cfrac{70}{100}\implies \cfrac{7000}{70}=x\implies \boxed{100=x}\\\\ -----------------------------$

$\bf A=100(0.7)^x\qquad \begin{array}{llll} x&y\\ \textendash\textendash\textendash\textendash\textendash\textendash&\textendash\textendash\textendash\textendash\textendash\textendash\\ 0&100\\ 1&70\\ 2&49\\ 3&34.3\\ 4&24.01\\ 5&16.807 \end{array}$