Step-by-step explanation: Answer is 10
For this type of problem, we need to create a slope intercept equation for both.
Let's start by making one for plan a. We know that there is 20 dollars per month, this is the y intercept. Now, although it says per month which can change by x, the problem is mainly asking for minutes.
Remember, a slope intercept equation is
y=mx+b
M is the slope, and x is multiplied to the slope. The slope for an example can be used for this, adam eats 5 apples per day or x, how many apples can he eat in 5 days? We are wanting to know how many he can eat in 5 days, so we of course would multiply 5 by 5. This is basically a slope equation.
So, for plan a, we have y=0.05x+20 where x is minutes
For plan b, we should get
y=0.10x+15 where x is also minutes. The problem is asking use to find which value that we plug in will make both plan a and b correct. Basically, the value we find is x, so we solve for x by setting the two equations equal.
0.05x+20=.10x+15 Use inverse operations
20=.05x+15
5=.05x
x=10
We know if we plug in 10 for x, both would equal the same or 21 dollars.
