Question

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 = -\frac{1}{6}
the subtraction property of equality
the multiplication property of equality
combining like - terms on one side of the equation
the distributive property

Explanation:

In line 2, we have \(-4x + 9=2x + 10\). To get to line 3 \(-6x+9 = 10\), we subtract \(2x\) from both sides of the equation. This is an application of the subtraction property of equality which states that if \(a=b\), then \(a - c=b - c\).

Answer:

the subtraction property of equality