Petra has 12 pound and ski has nothing. They both receive the same money for doing a delivery job.

Now Petra has three times as much as ski.

How much did they get for the job?

6 pounds

Step-by-step explanation:

Originally

Petra : 12 pounds

Ski: 0 pounds

Delivery job

Petra & Ski: Same amount.

Represent amount with 'D'

Total Amount

Petra: 12 + D pounds

Ski: D pounds.

Petra has three times as much as Ski, meaning

12 + D = 3 (D)

12 + D = 3D

12 = 3D - D

12 = 2D

Divide both sides by 2

6 = D ...