Find the greatest possible value for a+b+c+d if b is a positive integer and a, b,c, d satisfy the system of equations a+b=c

b+c=d

c+d=a

Step-by-step explanation:

The given system of equations is now reduced:

1) , , , Given

2) By 1)

3) 2) in 1)

4) By 1)

5) 4) in 3)

6) Algebra

7) Algebra

8) 7) in 4)/Algebra

9) 7) and 8) in 2)/Algebra

10) 9), 1), 7) and 8)/Algebra/Result

step-by-step explanation:

$54.99

step-by-step explanation:

$54.99 includes 500 min. if she does not exceed 500 min then her bill is $54.99