why sagemath returns 2 solution instead of one

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Sage gives the hand to Maxima to solve a Fourier-Motzkin list of inequalities. And if there is an explicit solution in equality terms Maxima gives it. Because if $x= 5$ necessarily $x<8$. There is no more to say. Try successively

solve([x <= 5, x<8],x)

solve([x < 5, x<8],x)