Insurance loss ratio calculation

Hi there

I am new to all things Power BI , and I am building some insurance reporting dashboards.

I am looking to build a dashboard which will allow me to calculate the loss ratio and triangles of a particular account. I have an excel file with the raw risk data and a excel file with the claims data (risk file shows the premium and claims file shows the claims). The common factor on both is the vehicle registration number.

What I would like to do, is to build a dashboard which matches the vehicle registration number on both files, and then calculates the loss ratio (claims divided by premium), as I would like to show this at portfolio level, but also at a more granular level.

I would also like to develop triangles, but again, not sure how I will need to do this.

I have not yet figured out how to calculate this, so if any one can help me, it would be appreciated!