Verified answer

[tex]\left \{ {{5x - 4y = 1 |*2} \atop {-2x + 5y = 20|*5}} \right. \\\\+\left \{ {{10x - 8y = 2} \atop {-10x + 25y = 100}} \right. \\17y=102\\y=102/17\\y=6\\5x-4*6=1\\5x=25\\x=5[/tex]