Answer:
Step 5
Step-by-step explanation:
The mistake is in step 5.
The previous step was

The order operations, PEDMAS, must be applied:
We have Addition and Division here,
Using PEDMAS, we must divide first to get:

We can now add to get:

Therefore the mistake occurred at step 5
Answer:
The distance PR is 21.6 Km
Step-by-step explanation:
Please find the attached document for explanation.
Also, I applied Cosine rule to determine the distance PR, since i have an angle (Q) in between two given sides of the triangle.