For this case we have that the generic equation of the line is given by:

Where,
m: slope of the line
b: intersection with the y axis.
Since the line is parallel to PQ, then the slopes are equal.
We have then:

On the other hand we have:

Substituting values we have:
Answer:
The equation of the line that is parallel to line PQ and that has the and intercept b = -3 is:
Answer:
76.7 liters
Step-by-step explanation:
You have ...
C1×V1 = C2×V2
so ...
V2 = V1×(C1/C2) = (115 L)×(14/21) = 76 2/3 L
V2 ≈ 76.7 L
There is no solution since 5 doesn't equal 45