I always find 10% of an amount , in your case I would then times the answer by 6. Half 10% and add them together- 10%=? 5%=? 60%=? 65%=?
1 lemonade.
2x+2=3x+1
-x+2=1
-x=-1
x=1 lemonade
I'm not really sure, because 650 marked down by 27% would be 474.5, which is close but not exact.
Hope I helped a little bit, sorry if I'm wrong.