C earned twice the amount that A did. So, assume C is 2 of A.
B earned $40 more than A did. So, if $40 is taken away from B's earning, B can be assumed another A as well. And the total sum is $340 (= 380 - 40).
Here, we can assume that there were 4 As, and each A earned the same amount, and the total was $340. So, each A earned $85 (= 340 ÷ 4).
Therefore, A made $85, B made $125 (=85+40), C made $170(=85x2) and 85+125+170=380. CKD.
The answer is: A earned $85.