The answer to this question has to be 8
Answer:

Step-by-step explanation:
100*2.2=220
80*2=176
220+176=396
So the two trains will take 2.2 hours so that they are 396 miles apart.
The hydronium ion is H₃O⁺ and its concentration is equivalent to the H⁺ ion concentration. The H⁺ ion concentration is given by:
pH = -log[H⁺]
[H⁺] = 10^(-8.2)
[H⁺] = 6.31 x 10⁻⁹ mole/dm³
The hydronium ion concentration is 6.31 x 10⁻⁹ mole/dm³