then you can make the source data into a Table and load it into the data model
then create 3 measures
X_Sum: =SUM(Table1[x])
All_X_Sum: CALCULATE([X_sum],all(Table1[op tijd]))
Yes_pct: =[X_sum]/[All_X_Sum]

and just add Yes_Pct to the data area then you can filter the 'op tijd' field to only show yes