Помогите, пожалуйста, решить систему [latex] \left \{ {{ \frac{1}{5} ^{4x-y}=25 } \atop {7 ^{9x-y}= \sqrt{7} }} \right. [/latex]

[latex] \left \{ {{ \frac{1}{5} ^{4x-y}=25 } \atop {7 ^{9x-y}= \sqrt{7} }} \right. \Rightarrow \left \{ {5^{y-4x}=5^2 } \atop {7 ^{9x-y}=7^{1/2}}} \right. \Rightarrow \left \{y-4x=2 } \atop {9x-y= \frac{1}{2} } \right. \Rightarrow[/latex] [latex] \left \{y=2+4x } \atop {9x-2-4x= \frac{1}{2} } \right. \Rightarrow \left \{y=2+4x } \atop {5x=2\frac{1}{2} } \right. \Rightarrow \left \{y=2+4x } \atop {x=0,5 } \right. \Rightarrow \left \{y=4 } \atop {x=\frac{1}{2} } \right.[/latex]