Carla and Rob left a 20 percent tip after having lunch at a restaurant. The amount of the tip was 6$. Carla's lunch cost $15. Write an equation you can use to find x, the cost of Robs lunch.

Rob lunch costs $15 and an equation that can be used to compute it is x = y - 15, where y is the total amount of the bill minus the tip, that is y = 6/0.2

Step-by-step explanation:

In order to solve this question we can attribute a variable to the total amount spent on this lunch, we'll call it "y". The problem states that a 20% tip was given after lunch and that this value was $6. From this information we can calculate the value of "y". We have:

20%*y = 6

(20/100) * y = 6

0.2*y = 6

y = 6/0.2 = $30

Then the problem tells us that Carla's lunch was $15, so we can calculate the value that Rob spent that will be:

x = 30 - 15 = $15

An equation that can be used to find Rob's lunch value is:

x = y - 15

Since we know that y = 6/0.2 we have:

x = 6/0.2 - 15 = 30 - 15