$Raskite\ x,\ jei\ \ \ \ \frac{70}{5}=\frac{x}{15}$  

 $Raskite\ x,\ jei\ \ \ \frac{12}{7}=\frac{2x}{10}$  

 $Raskite\ x,\ jei\ \ \ \ \frac{x+3}{7}=\frac{12}{5}$  

 $Raskite\ x,\ jei\ \ \ \frac{9}{5}=\frac{2x-1}{8}$