d=number of drinks
p=number of bags of popcorn
75=6d+8p
100.50=12d+10p
multiply first equation by -2 and add to first
-49.50=-6p
divide -6
8.25=p
sub
100.50=12d+10p
100.50=12d+82.50
minus 82.50
18=12d
divide 12
1.50=d
$1.50 per drink
YOU BETTER READ AND LEARN AND NOT JUST USE THIS TO PASS, LEARN