Respuesta :

ElenaClaudia
Hello from Romania! 

[tex](x+y)^2 = 49 \\ x+y= \sqrt{49} \\ x+y=7 \\ \\ (x-y)^2=9 \\ x-y= \sqrt{9} \\ x-y=3 \ \ \ \ \Rightarrow y=x-3 \\ \\ x+y=7 \\ x+x-3=7 \\ 2x-3=7 \\ 2x=10 \\ \boxed{x=5}[/tex]

Good luck!