Question 121115
Let {{{b}}} = total monthly bill in cents
c = number of local calls
l = number of long distance calls
{{{b = 2400 + 20c + l}}}
{{{4593 = 2400 + 20c + 1633}}}
{{{20c = 4593 - 2400 - 1633}}}
{{{20c = 560}}}
{{{c = 28}}}
She made 28 local calls