Question

Pls answer questions 12 and 13

Answer 1

12) 

$\bf \begin{array}{cccccclllll} \textit{something}&&\textit{varies directly to}&&\textit{something else}\\ \quad \\ \textit{something}&=&{{ \textit{some value}}}&\cdot &\textit{something else}\\ \quad \\ y&=&{{ k}}&\cdot&x \\ && y={{ k }}x \end{array}\\\\ -----------------------------$

$\bf \textit{we know that } \begin{cases} x=20\\ y=4 \end{cases}\implies 4=20k \\\\\\ \cfrac{4}{20}=k\implies \cfrac{1}{5}=k\qquad thus\implies y=\cfrac{1}{5}x\\\\ -----------------------------\\\\ \textit{what is "y" when x = 35?}\implies y=\cfrac{1}{5}\cdot 35$

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13)

$\bf \begin{array}{llllll} \textit{something}&&\textit{varies inversely to}&\textit{something else}\\ \quad \\ \textit{something}&=&\cfrac{{{\textit{some value}}}}{}&\cfrac{}{\textit{something else}}\\ \quad \\ y&=&\cfrac{{{\textit{k}}}}{}&\cfrac{}{x} \\ &&y=\cfrac{{{ k}}}{x} \end{array}\\\\ -----------------------------$

$\bf \textit{now, we know again that } \begin{cases} x=20\\ y=4 \end{cases}\implies 4=\cfrac{k}{20} \\\\\\ 4\cdot 20=k\implies 80=k\qquad thus\implies y=\cfrac{80}{x}\\\\ -----------------------------\\\\ \textit{what's "y" when x=35?}\qquad y=\cfrac{80}{35}$