Answer:
a) 333,33 b)291,67
Explanation:
you have both equations :
C=50+0.5V and V=2500-10C
and you want to know the variable V so, you can calculate V in function of C, and you have already clear the variable "C", then you replace for (a):
for b) they tell you that you increase your constant of the equiation C=50+0.5V (remember that the constant is the one alone, wihout any variable, in this case "50") increase in 25 so, your equiation for this point of C is C=75+0.5V, then you do the same:
It's a system of two equations and two variables, wich gives you a compatible define system, it gives you only one solution.
I hope it helps you.