A fisherman 's spring scale is extended to a total length of 0.18 m when a 6.12 kg fish is suspended from it .?

Hookes Law F = -kX = mg

A fisherman 's spring scale is extended to a TOTAL length of 0.18 m... This part is tricky, it is not X, it's the total length, where X is the length of the extension in the spring.

To find X, you need to find how long the spring is at rest. You can do this with the data for fish #1...

F = mg = (6.12kg)(9.8m/s²) = 59.97N = -kX = -1000N/m*X
X = F/k = 59.97N/1000N/m = 0.059m = 0.06 m

For fish #2 you can find X now...

F = mg = (11.4kg)(9.8m/s²) = 111.7N = -kX = -1000N/m*X
X = F/k = 111.7N/1000N/m = 0.059m = 0.11 m

The spring at rest is equal to 0.18m - 0.06m = 0.12m

The total length for fish #2 = 0.12m + 0.11m = 0.23m