a)\(\frac{x}{15}=\frac{2}{5}\)=> x=\(\frac{15.2}{5}=6\)
b) \(\frac{3}{x^7}hay\frac{3}{x.7}\)
a)\(\frac{x}{15}=\frac{2}{5}\Rightarrow x=\frac{2\cdot15}{5}=6\)
b)\(\frac{3}{x\cdot7}=\frac{27}{135}\Rightarrow x\cdot7=\frac{3\cdot135}{27}\Rightarrow x\cdot7=15\Rightarrow x=2\frac{1}{7}\)