Question

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Answer 1

let me take first equation
x-2y= 5
3 -2(-1)=5
3+2=5
5=5 so (3,-1)is the solution for the equation x-2y=5

second equation :
2x-y=7
2(3)-(-1)=7
6+1=7
7=7 so (3,-1)is the solution of this equation also that is of 2x-y=7