Answer: $0.36
Explanation:
Given : You buy butter for $3.31 a pound.
i.e. cost of 1 pound of butter = $3.31
Also, 1 pound = 16 oz
Using UNITARY METHOD ,
1 oz =

i.e. cost of 1 oz of butter = 0.0625 x cost of 1 pound of butter
0.0625 x $3.31 =$ 0.206875 ≈ $0.21
One portion of the onion compote requires 1.7 oz of butter.
The cost of 1.7 oz of butter = 1.7 x cost of 1 oz of butter
1.7 x $ 0.21= $0.357≈ $0.36 [Rounded to the nearest cent]
Hence, the butter for one portion costs $0.36 .