Question

ofer coroana! URGENT​

Answer 1

$\displaystyle a)~\frac{x}{2,8} =\frac{1,05}{0,7} \Rightarrow \frac{x}{\cfrac{28}{10} } =\frac{\cfrac{105}{100} }{\cfrac{7}{10} } \Rightarrow x\cdot \frac{10}{28} =\frac{105}{100} \cdot \frac{10}{7} \Rightarrow \frac{10x}{28} =\frac{105}{70} \Rightarrow \\\\ \Rightarrow 10x \cdot 70=105 \cdot 28 \Rightarrow 700x=2940 \Rightarrow x=\frac{2940}{700}\Rightarrow x= \frac{21}{5}$

$\displaystyle b)~\frac{14}{x} =\frac{2,1}{0,54} \Rightarrow \frac{14}{x} =\frac{\cfrac{21}{10} }{\cfrac{54}{100} } \Rightarrow \frac{14}{x} =\frac{21}{10} \cdot \frac{100}{54} \Rightarrow \frac{14}{x} =\frac{210}{54}\Rightarrow \\\\\Rightarrow 14 \cdot 54=210 \cdot x \Rightarrow 756=210x\Rightarrow x=\frac{756}{210} \Rightarrow x=\frac{18}{5}$

$\displaystyle c)~\frac{0,42}{1,5} =\frac{x}{35} \Rightarrow \frac{\cfrac{42}{100} }{\cfrac{15}{10} } =\frac{x}{35}\Rightarrow \frac{42}{100} \cdot \frac{10}{15} =\frac{x}{35} \Rightarrow \frac{42}{150} =\frac{x}{35}\Rightarrow \\\\ \Rightarrow 42 \cdot 35=x \cdot 150 \Rightarrow 1470=150x \Rightarrow x=\frac{1470}{150} \Rightarrow x=\frac{49}{5}$

$\displaystyle d)~\frac{2,8}{0,84} =\frac{16}{x} \Rightarrow \frac{\cfrac{28}{10} }{\cfrac{84}{100} } =\frac{16}{x} \Rightarrow \frac{28}{10} \cdot \frac{100}{84} =\frac{16}{x} \Rightarrow \frac{280}{84}=\frac{16}{x} \Rightarrow \\\\ \Rightarrow 280 \cdot x=16 \cdot 84 \Rightarrow 280x=1344 \Rightarrow x=\frac{1344}{280} \Rightarrow x=\frac{24}{5}$