Answer:
Two conversion factors:

Explanation:
You can create two possible <em>conversion factors</em>, one to convert from mL to L, and one to convert from L to mL
<u />
<u>a) From mL to L</u>
To convert mL to L you need to multiply by a conversion factor that has mL on the denominator and L in the numerator.
Your starting point is: 
Then, divide both sides by 1,000mL (this will be on the denominator of the fraction);

<u>b) From L to mL</u>
Divide both sides by 1 L:

Answer:
30 Liters of 40% acid solution and 10 L of 60% acid solution is needed.
Explanation:
Let volume of the 40% acid solution be x.
Let volume of the 60% acid solution be y.
Volume of solution formed after mixing both solution = 40 L
x + y = 40 L..[1]
Volume of acid 40% solution = 40% of x= 0.4x
Volume of acid 60% solution = 60% of y= 0.6y
Volume of acid formed = 45% of 40 L = 
..[2]
Solving [1] and [2]
x = 30 L , y = 10 L
30 Liters of 40% acid solution and 10 L of 60% acid solution is needed.
The oxidation of at least two atoms should change
The answer is prolly A or B