To find out which fish Sasha bought, we first need to determine how much she spent per pound based on the weight of fish she purchased.
Sasha bought 3/4 lb. of fish for $5.40. To find the price per pound, we divide the total cost by the weight she bought:
\[ \text{Price per pound} = \frac{\text{Total cost}}{\text{Weight}} = \frac{5.40}{\frac{3}{4}} = 5.40 \times \frac{4}{3} = \frac{21.6}{3} = 7.20 \]
So, the price per pound of the fish Sasha bought is $7.20.
Now, we can compare this price to the prices of the fish available:
- Salmon: $9.60 per pound
- Whitefish: $7.20 per pound
- Swordfish: $8.40 per pound
- Haddock: $6.90 per pound
Since the price per pound for the fish Sasha bought is $7.20, it matches the price of whitefish. Therefore, Sasha chose:
Whitefish.