Finding Potential Difference between two points

[Knah]

Homework Statement

Homework Equations

V=IR (Voltage = Current x Resistance)
Possibly Kirchoff's Loop Rule but I'm not really sure how to use it

The Attempt at a Solution

I looked at something else on line and ended up doing 9 - 0.7(3) - 6 - 2(3) which got me the right answer for the first part but I don't really what I did and if that is the proper way to solve the problem so any explanation/correction for that would be great. For the second part, I had no idea.

 

[mukundpa]

Hi,
Need not to complete the loop, As we know the current in the branch start from point B (considering V_B = 0 and move towards A and see the voltage is dropped or gained and add accordingly. As the current is to the right the voltage will increased on the left side of R (= IR) and then decrease due to cell by by 9 V and so on.