Yup D is the answer if
For example if 6 was X you would do 2(6)-10 that would get you 10
then do 4(6)+1 that would get you 25 do 25+25+10+10 that gets you 54
now check your work do 12(6)-18 that gets you 54 and that is correct
The answer is 12(X)-18 or D