Question

x pe y egal cu 7 pe 2, 3x+5y pe 2x+y

Answer 1

x/y=7/2
=> x=7k
=> y=2k

3x+5y supra 2x+y=
3•7k+5•2k supra 2•7k+2k=
21k+10k supra 14k+2k=
31k supra 16k=
31 supra 16

Answer 2

$\displaystyle\frac{x}{y}=\frac{7}{2}\implies 2x=7y=k \\ \\ x=\frac{k}{2} \\ \\ y=\frac{k}{7} \\ \\ \frac{3x+5y}{2x+y}= \\ \\ \frac{\frac{3k}{2}+\frac{5k}{7}}{k+\frac{k}{7}}= \\ \\ \frac{\frac{21k+10k}{14}}{\frac{8k}{7}}=\frac{31k}{14}\times\frac{7}{8k}=\frac{31}{16}$