We have to try them all out and see:

Let's try A (3,-2)

That means to substitute (3) for x and (-2) for y
in this equation and simplify:

     2x - y = 8
2(3) - (-2) = 8
      6 + 2 = 8
          8 = 8

That's true so A (3,-2) is the correct answer.
But let's see why the others are not the answer:

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Let's try B (-2,6)

That means to substitute (-2) for x and (6) for y
in this equation and simplify:

     2x - y = 8
2(-2) - (6) = 8
     -4 - 6 = 8
        -10 = 8

That's false so B (-2,6) is not the correct answer.

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Let's try C (-3,-2)

That means to substitute (-3) for x and (-2) for y
in this equation and simplify:

     2x - y = 8
2(-3) - (-2) = 8
     -6 + 2 = 8
         -4 = 8

That's false so B (-3,-2) is not the correct answer.

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Let's try D (-2,-6)

That means to substitute (-2) for x and (-6) for y
in this equation and simplify:

      2x - y = 8
2(-2) - (-6) = 8
      -4 + 6 = 8
           2 = 8

That's false so D (-2,-6) is not the correct answer.

Edwuin