Beth and Billy are biking to their friend Bernie’s house. After 1 mile, Beth and Billy have traveled 4/5 of the total distance to Bernie’s house. How much farther do Beth and Billy have to go in order to arrive at Bernie’s?

Step-by-step explanation:

 Let be "x" the total distance in miles that Beth and Billy have to cover to arrive to Bernie's house.

Based to the information given in the exercise, you know that after 1 mile Beth and Billy traveled of "x". Then, you can write the following equation:

Now you must solve for "x" in order to find its value. This is:

Let be "y" the remaining distance (in miles) that Beth and Billy have to go in order to arrive at Bernie's house. This is represented by:

Therefore, substituting the value of "x" into the equation and evaluating, you get the following result:

the first one, all those points on the line just make a strait line.