Question 1104877
let x equal the number of minutes.


spirit charges 10 + .05 * x.


horizon charges .15 * x


she wants to compare what spirit charges versus what horizon charges and where the break even point would be.


at least i think that's what she wants to do.


both plans will break even when the cost for each plan is the same.


the cost for spirit is 20 + .05 * x


the cost for horizon is .15 * x.


when the cost is even, then 20 + .05 * x = .15 * x


subtract .05 * x from both sides of this equation to get 20 = .10 * x


divide both sides of this equation by .10 to get 20 /.10 = x


solve for x to get x = 200.


the plans will break even when the number of minutes used per month = 200.


if she uses less than 200 minutes, the horizon plan is cheaper.


if she uses more than 200 minutes, the spirit plan is cheaper.


your system of equations is:


cost for spirit plan = 20 + .05 * x.
cost for horizon plan = .15 * x


we'll look at a couple of sample figures.


100 is less than 200.
cost for spirit is 20 + .05 * 100 = 25.
cost for horizon is .15 * 100 = 15.
horizon is cheaper.


200 is equal to 200.
cost for spirit is 20 + .05 * 200 = 30
cost for horizon is .15 * 200 = 30
they break even.


300 is greater than 200.
cost for spirit is 20 + .05 * 300 = 35
cost for horizon is .15 *300 = 45
spirit is cheaper.