Difference , the % of difference and average

Hi,

I am under intermidiate user of Power Bi and I need your help.

the file that I work on is for POs; so the original table named " POs".

I have three columns:

1- Quantity ordered.

2- PO Value in Local Currency ( for all quantities ) 

3- Price in Purchase Requisition ( the price for 1 quantity)

the benefitiary initiates PR and puts estimation price, then after bidding, the PO is issued. I calculated in excel the following:

•   PRICE ESTIMATION ACCURACY = 3-2/1
• PRICE ESTIMATION ACCURACY %= PRICE ESTIMATION ACCURACY/ Price in Purchase Requisition
• The average of PRICE ESTIMATION ACCURACY %

How can I do the same in Power Bi using Measures, not created Columns, if possible.

Thanks.