To find the equation that represents the number of residents surveyed, we know that two-fifths of the total number of respondents \( r \) equals 80 residents who like the beach. This can be expressed as:
\[ \frac{2}{5} r = 80 \]
Now, we can solve for \( r \) to find out how many residents were surveyed. To do this, multiply both sides of the equation by \( \frac{5}{2} \):
\[ r = 80 \times \frac{5}{2} \]
Calculating that gives:
\[ r = 80 \times 2.5 = 200 \]
So the total number of residents surveyed is \( 200 \).
The correct response is:
\[ \frac{2}{5}r=80; \text{ 200 residents were surveyed.} \]