Ximena and Darius left a 20% tip after having dinner at a restaurant. The amount of the tip was $5. Ximena’s dinner cost $15. Which equation can you use to find x, the cost of Darius’s dinner?

0.2 (15+x) = 5

Step-by-step explanation:

Let 'x' represent  cost of Darius’s dinner

Ximena’s dinner cost $15, that will be added to cost of Darius's lunch i.e 'x'.  They left a 20% tip on the TOTAL cost of both their lunches that would be equal $5.  So, the equation is 5=0.2(x+15). 20% (0.2) of the sum of Ximena and Darius lunches i.e 5 dollars.

Equation : 0.2 (15+x) = 5

(0.2) (15) + 0.2x = 5

             3 + 0.2x = 5

                   0.2x = 2

                         x = 2/0.20

                         x = 10

Darius’s dinner  cost $10

Verification :  

15+10=25

25 x 0.20 = 5

1)

2)

3) x=2

For this case if we see the second step Mark subtract 8 from the left part of the equation but not subtract 8 from the right side of the equation, and that's an error.

So then the correct answer for this case would be:

C.  To balance the equation, Mark should also subtract 8 from the right side of the equation in step 2.

2)

3)

Step-by-step explanation:

For this case we have the following equation:

And Mark's use the following procedure to solve it:

1)

2)

3) x=2

For this case if we see the second step Mark subtract 8 from the left part of the equation but not subtract 8 from the right side of the equation, and that's an error.

So then the correct answer for this case would be:

C.  To balance the equation, Mark should also subtract 8 from the right side of the equation in step 2.

2)

3)