[tex] a)\frac{2x}{3y} = \frac{5}{7} => \frac{x}{y} = \frac{5\cdot 3}{7\cdot 2} => \frac{x}{y} = \frac{15}{14}\\
b) \frac{x}{y} = \frac{15}{14}=>\frac{x-y}{y} = \frac{15-14}{14}=>\frac{10}{y} = \frac{1}{14}=>\\
y=140\\
x-140=10\\
x=10+140\\
x=150[/tex]