Question

write a system of equations in two variables that has (5, -1) as its only solution

Answer 1

x = 5, y = -1
Let us consider one equation as: x + y = 5 + (-1) = 4
Another equation could be: 2x + y = 2(5) + (-1) = 10 - 1 = 9

So the two equations are:
x + y = 4
2x + y = 9

Answer 2

That is just one set of equations. There are infinite such sets that will all yield (5,-1) as its only solution.

Answer 3

Thanks

Answer 4

You are welcome.