Question 416559
You can start by writing the appropriate equation for the total cost (C) of Sarah's telephone service.
{{{C = 21+0.25x+D}}} where x = the number of local calls at $0.25 each and D = the cost of the long-distance calls.
Substitute into equation above: C = $34.64 and D = $6.14
{{{34.64 = 21+0.25x+6.14}}} Simplify and solve for x.
{{{34.64 = 21+6.14+0.25x}}}
{{{34.64 = 27.14+0.25x}}} Subtract 27.14 from both sides.
{{{7.50 = 0.25x}}} Divide both sides by 0.25
{{{30 = x}}}
Sarah made 30 local calls.