The formula for that one is:

 

thrust - drag divided by weight times 100.

 

which thrust is 28000*3engines : 84000N

 

weight is 50000kg : 500000N

 

drag is W/ LD ratio :500000/12 : 41667

 

so would be 84000-41667 / 500000 *100 : 8.46 is 8.5%