To find the number of residents surveyed, \( r \), given that two-fifths of the respondents (which is \( \frac{2}{5} \) of the total) equals 80 residents, we can set up the equation:
\[ \frac{2}{5} r = 80 \]
Now let's solve for \( r \):
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Multiply both sides by 5 to eliminate the fraction: \[ 2r = 80 \times 5 \] \[ 2r = 400 \]
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Now, divide both sides by 2: \[ r = \frac{400}{2} \] \[ r = 200 \]
So, the correct equation is \( \frac{2}{5} r = 80 \), and the total number of residents surveyed is 200.
Thus, the answer is: \[ \frac{2}{5} r = 80; , 200 \text{ residents were surveyed.} \]