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# the average of 3 numbers is 7. Two of the numbers are 8 and 9. What is the 3rd?

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the average of 3 numbers is 7. Two of the numbers are 8 and 9. What is the 3rd?

Guest May 27, 2015

#1
+10

$${\frac{\left({\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}}\right)}{{\mathtt{3}}}} = {\mathtt{7}}$$

$${\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}} = {\mathtt{21}}$$

$${\mathtt{x}} = {\mathtt{21}}{\mathtt{\,-\,}}{\mathtt{8}}{\mathtt{\,-\,}}{\mathtt{9}}$$

$${\mathtt{x}} = {\mathtt{4}}$$

Guest May 27, 2015
Sort:

#1
+10

$${\frac{\left({\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}}\right)}{{\mathtt{3}}}} = {\mathtt{7}}$$

$${\mathtt{x}}{\mathtt{\,\small\textbf+\,}}{\mathtt{8}}{\mathtt{\,\small\textbf+\,}}{\mathtt{9}} = {\mathtt{21}}$$

$${\mathtt{x}} = {\mathtt{21}}{\mathtt{\,-\,}}{\mathtt{8}}{\mathtt{\,-\,}}{\mathtt{9}}$$

$${\mathtt{x}} = {\mathtt{4}}$$

Guest May 27, 2015
#2
+91436
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