Answer: Choice A. (8, 4)
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Step-by-step explanation:
Because x = 2y, we can replace every copy of x with 2y
Let's do so in the second equation
3x - 4y = 8
3(x) - 4y = 8
3(2y) - 4y = 8 .... x replaced with 2y; now let's isolate y
6y - 4y = 8
2y = 8
y = 8/2 ..... divide both sides by 2
y = 4
Use this y value to find x
x = 2y
x = 2*4
x = 8
So we have x = 8 and y = 4 pair together to get the answer (x,y) = (8, 4) which is choice A.