The graph was made to compare the costs of taking two different taxis. What does the intersection mean for the two lines?

The total price of $8 is the same for both taxi cabs for 3 miles.

Step-by-step explanation: if you look at the graph you can see the dot on 8(which is the total cost) and the number of miles is 3

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.