Question 755791
from 7x-4y=9 we get
{{{
x=(4y+9)/7
}}}

{{{
-3(4y+9)/7+5y=-17
}}}


m7:

{{{
-3(4y+9)+35y=-119
}}}


y=(-119+27)/(35-12)=-4


so that means


{{{
x=(4y+9)/7=(4(-4)+9)/7=-1
}}}


:)