What is the justification for the step taken from line 2 to line 3?
3x +9-7X=X+10+X
-4x+9 = 2x+10
-6x+9= 10
-6x=1
x = 6 음
(A) the subtraction property of equality
(B) the multiplication property of equality
(C) combining like terms on one side of the equation
(D) the distributive property
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step-by-step explanation:

the ratio of red paint to blue paint is always 9/7. that means that, whatever x's value, (4x+12)/(4x-4) has that same ratio. so, set up an equation and cross-multiply to solve for x:

9/7 = (4x+12)/(4x-4)

9(4x-4) = 7(4x+12)

36x - 36 = 28x + 84

8x - 36 = 84

8x = 120

x = 15