# Evaluating a variable expression

a=4,b=3 and c=-2

5ab/12-2cb

#### MarkFL

Staff member
As posted, it is hard to tell if you mean:

$\displaystyle \frac{5ab}{12}-2cb$

or

$\displaystyle \frac{5ab}{12-2cb}$

Until you learn to use $\LaTeX$, I recommend you use bracketing symbols to make it clear exactly what the denominator is.

If the first choice above is what you intend, then you could type (5ab/12) - 2cb, and if the second choice is what you intend, then you could type (5ab)/(12 - 2cb).

Do you see how that removes the potential ambiguity?

#### rodgerst414

##### New member
As posted, it is hard to tell if you mean:

$\displaystyle \frac{5ab}{12}-2cb$

or

$\displaystyle \frac{5ab}{12-2cb}$

Until you learn to use $\LaTeX$, I recommend you use bracketing symbols to make it clear exactly what the denominator is.

If the first choice above is what you intend, then you could type (5ab/12) - 2cb, and if the second choice is what you intend, then you could type (5ab)/(12 - 2cb).

Do you see how that removes the potential ambiguity?
it is the first one i just don't know how to put them in the calculator or write them on here.

#### MarkFL

Staff member
Okay, you have technically written it correctly then, but there are so many students who would write what you did when they mean the second choice, that it is best to make sure.

Now, given what I told you in your first topic, what do you think you need to do here as the first step?

#### rodgerst414

##### New member
it is the first one i just don't know how to put them in the calculator or write them on here.
It is the first on you wrote how do you put into a calculator.

#### rodgerst414

##### New member
Okay, you have technically written it correctly then, but there are so many students who would write what you did when they mean the second choice, that it is best to make sure.

Now, given what I told you in your first topic, what do you think you need to do here as the first step?
Sorry but this is my first time to do these problems i don't understand.I quit school at a younger age. i am 41 first time in college.This is this the class they put me in.Can you recommend some books for me to learn these kinds of problems.