We can write an equation based on the information in the problem.
y=mx+b is the skeleton for our equation.
We can think of b as our starting point, the very least we can be charged. The problem tells us our base fee is $15.99 and that they add on $.18 for every additional minute.
So b is 15.99, and m is our rate, which is .18. Now w just need to figure out where that 48 goes. It can either be the x or the y.
In math, x is the independent variable and y is the dependent variable. Those might sound like big, science-y words, but they basically mean that a change is y is cause by x. In this case, the more minutes are use, the money the phone is charged.
So minutes change money. That means x is minutes and y is money.
48 is the number of minutes spent talking,s o we're solving for y or money:
y=15.99+48(.18)
y=15.99+8.64
y=24.63 or $24.63
