You can easily test this if you know that (6, -10) corresponds to (X, Y). Knowing this, you can:
X = 6
Y = -10
you put this into your equation:
-10 = 3*6 - 8
calculate it:
-10 = 18 - 8
-10 = 10
This is not true of course, -10 is not equal to 10. Therefore, (6, -10) is not a solution of y = 3x-8 :)
The answer is 6 cause 9-5 is 4 and 20/4 equal 5+1 equal 6
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X= 3r+5/2 is the answer I believe