Needed Score?

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Two young mathematicians examine an equation.

Check out this dialogue between two calculus students (based on a true story):

Devyn: Riley, I have a question.
Riley: What’s on your mind?
Devyn: Suppose we have three exams.
Riley: Ok.
Devyn: On the first, I scored 74/100, and on the second I scored 84/100.
Riley: Not bad! What’s the question, though?
Devyn: What do I need to get on the third exam to average an 82% overall?
Riley: To find the average of three numbers, you add them and divide the sum by three.
Devyn: Yes, but how do I figure out how to get an 82%?

Let’s call Devyn’s score on midterm 3 as $x$ . According to Riley, Devyn’s exam average would be $\frac {74 + 84 + x}{3}.$

In order to determine what score Devyn needs on his last exam,they will need to setup and solve an equation involving this expression.

Is the following an equation: $\displaystyle \dfrac {74 + 82 + x}{3}$ ?

Remember that equations need an equals sign. Without one, it is just an expression.

Press...	...to do
left/right arrows	Move cursor
shift+left/right arrows	Select region
ctrl+a	Select all
ctrl+x/c/v	Cut/copy/paste
ctrl+z/y	Undo/redo
ctrl+left/right	Add entry to list or column to matrix
shift+ctrl+left/right	Add copy of current entry/column to to list/matrix
ctrl+up/down	Add row to matrix
shift+ctrl+up/down	Add copy of current row to matrix
ctrl+backspace	Delete current entry in list or column in matrix
ctrl+shift+backspace	Delete current row in matrix

Type...	...to get
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sqrt	$\sqrt{\blue{[?]}}$
paren	$\left(\blue{[?]}\right)$
floor	$\lfloor \blue{[?]} \rfloor$
factorial	$\blue{[?]}!$
exp	${\blue{[?]}}^{\blue{[?]}}$
sub	${\blue{[?]}}_{\blue{[?]}}$
frac	$\dfrac{\blue{[?]}}{\blue{[?]}}$
int	$\displaystyle\int{\blue{[?]}}d\blue{[?]}$
defi	$\displaystyle\int_{\blue{[?]}}^{\blue{[?]}}\blue{[?]}d\blue{[?]}$
deriv	$\displaystyle\frac{d}{d\blue{[?]}}\blue{[?]}$
sum	$\displaystyle\sum_{\blue{[?]}}^{\blue{[?]}}\blue{[?]}$
prod	$\displaystyle\prod_{\blue{[?]}}^{\blue{[?]}}\blue{[?]}$
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vec	$\left\langle \blue{[?]} \right\rangle$
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*	$\cdot$
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arccos	$\arccos\left(\blue{[?]}\right)$
arctan	$\arctan\left(\blue{[?]}\right)$
sin	$\sin\left(\blue{[?]}\right)$
cos	$\cos\left(\blue{[?]}\right)$
tan	$\tan\left(\blue{[?]}\right)$
sec	$\sec\left(\blue{[?]}\right)$
csc	$\csc\left(\blue{[?]}\right)$
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Delta	$\Delta$
Theta	$\Theta$
Lambda	$\Lambda$
Xi	$\Xi$
Pi	$\Pi$
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Phi	$\Phi$
Psi	$\Psi$
Omega	$\Omega$

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