Question 1089986
We need to start by setting up an equation for the monthly cost of each plan. To do this we need to name a variable for the number of minutes, let's say x. Let's call the first plan A and the second plan B.  Then if the first plan has a $17 monthly fee and $0.08 per minute, we can represent that as:
{{{A = 17 + 0.08x}}}
The second plan is $9 monthly plus $0.13 per minute, so 
{{{B = 9 + 0.13x}}}
The question is asking when they will be the same, so we literally set them equal to each other.
{{{17 + 0.08x = 9 + 0.13x}}}
Subtracting 9 to the left, and 0.08x to the right, we have
{{{8 = 0.05x}}}
Lastly, by dividing both sides by 0.05, we get
{{{x = 160}}}
So the cost of the two plans will be equal when the number of minutes is 160.