Because there are no grouping symbols around the denominator, your typing means this:

\(\displaystyle a = c - \dfrac{d}{2} \; \cdot \; e\)

I'm thinking maybe you meant this, instead:

a = c - d/

(2e

)
These grouping symbols show that 2e is a denominator:

\(\displaystyle a = c - \dfrac{d}{2e}\)

It's important to type grouping symbols around numerators or denominators that contain more than one number or symbol. Otherwise, people can't be sure which way to go.

So, what happened, when you substituted the given values for the given symbols? Did you then try the arithmetic? For example, the equation c=20 tells us that we can replace symbol c with the number 20, anywhere we see it. That's called 'substitution'. Once you substitute all of the given values, do the arithmetic.

Need more help? Please show us what you tried (even if you think it's wrong).

Also, be sure to read

**the forum guidelines**.

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**Here's a short video lesson.**
[video=youtube_share;S_OX3ByvBSc]https://youtu.be/S_OX3ByvBSc[/video]