Answer:
370 millimeters of compound B is needed for 666 millimeters of solution.
Explanation:
Given that:
4 millimeters of compound A are used for every 5 millimeters of compound B.
The scientist wants to make 666 millimeters of solution.
Let,
x be the multiplier number of the compounds in the solution.
Then,
4x + 5x = 666
9x = 666
Dividing both sides by 9

Millimeters of compound B = 5x = 5(74) = 370 millimeters
Hence,
370 millimeters of compound B is needed for 666 millimeters of solution.