Question

It costs a flat fee of $3.15 to make an international call plus $0.05 for every minute that you talk. If you were charged $5.10 for making an international call, for how many minutes did you talk?
minutes

Answer 1

y = 0.05x + 3.15 with y being the total cost and x being the number of minutes

so if u were charged 5.10.....sub in 5.10 for y
5.10 = 0.05x + 3.15
5.10 - 3.15 = 0.05x
1.95 = 0.05x
1.95 / 0.05 = x
39 = x <=== so u talked for 39 minutes

Answer 2

Answer: 39 minutes.

Step-by-step explanation:

You can solve this in two different ways:

(1) You subtract the flat fee from the final charge to get how much was spent in additional fees and then do a rule of three:

$5.10-3.15=1.95$

$0.05 --------- 1 minute

$1.95 ---------- x

$x=\frac{1.95*1}{0.05} =39minutes$

(2) You can raise an equation that represents the situation:

$y=3.15+0.05x$

where "y" is the total charge for the call and "x" is the number of minutes that you talk.

In this case, the total charge for the call is $5.10 and the unknown variable is the number of minutes, so you have to isolate the x:

$5.10=3.15+0.05x\\0.05x=5.10-3.15\\x=\frac{1.95}{0.05} =39minutes$