B is the only rational answer.
Answer: 18
<u>Do Keep Change Flip (KCF)</u>
Keep: 9/2
Change: ÷ into ×
Flip: 1/4 into 4/1
Your new problem should be 9/2×4/1
<u>Multiply</u>
9/2×4/1=36/2
36/2=18
Final Answer: 18
You add half of the coefficient of x and square it.
What you do on one side,you must do it on the other.
3(x + 7) = 9(x - 1)
3(x) + 3(7) = 9(x) - 9(1)
3x + 21 = 9x - 9
<u>- 3x - 3x </u>
21 = 3x - 9
<u>+ 9 + 9</u>
<u>30</u> = <u>3x</u>
3 3
10 = x