Help please

[CharlieHorse]

I need an explanation, step by step on this problem. It's a practice sheet and I know the answer I just need to know how to get there.

If 3x-d=c, then x=

A) c+d-3 B) d+c/3 C) (d-c)/3 D) (c-d)/3 E) (c+d)/3

I keep plugging in the answer choices for x but I keep getting 2 choices that work.
Thank you so much!

 

[mmm4444bot]

I keep plugging in the answer choices for x but I keep getting 2 choices that work.

If you're thinking that the following expressions are the same (they are not), then your issue has to do with the Order of Operations.

d + c/3

(d + c)/3

In the first case, the division is done first; in the second case, the addition is done first.



If you had shown your work for each of the two results you reference, then we could have told you what you're doing wrongly. (Please read the post titled "Read Before Posting".)

The steps are:

1) Add d to both sides

2) Divide both sides by 3

Cheers ~ Mark :cool:

 

[CharlieHorse]

Oh wow *face palm* I was trying to plug in the equations for x when all they wanted me to do was isolate x.

Thank you!

 

[mmm4444bot]

Ah, yes. The question "x=?" means solving for x.

PS: The multiple choices are not equations. Equations always contain an equals sign. The correct word for those multiple choices is "expressions". :cool: