Answer
Find out the what is her monthly fixed charge .
To prove
Let us assume that the cost per mintues = x
Let us assume that the monthly charge be = y
As given
n Chatty Cathy’s cell phone plan she pays for minutes used plus a fixed monthly charge.
For 500 minutes she pays $35 total
Than the equation becomes
500x + y = 35
As given
for 1500 minutes used she pays $55 total.
Than the equation becomes
1500x + y = 55
Subtracted 500x + y = 35 from 1500x + y = 55
1500x - 500x + y - y = 55 - 35
1000x = 20
x = $0.02
Put in the 500x + y = 35
500 × 0.02 + y = 35
10 + y = 35
y = 35 - 10
y = $25
Therefore the monthly fixed charge be $25.