Abridge has been constructed between the mainland and
anisland. the total cost (excluding toll) to travel across
thebridge is expressed as c=50+0.5v, where v is the number of
veh/dayand c is the cost/vehicle in cents. the demand for
travelacross the bridge is v=2500-10c.
(a)determine the volume of traffic across the bridge.
(b)if a toll of 25 cents is added, what is the volume
acrossthe bridge?

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.