The members of the drama club sold a total of 840 adult and student tickets to their spring play. the number of adult tickets they sold was 120 less than twice the number of student tickets sold. how many of each type of ticket did the drama club sell?

A=number of adult tickets
s=number of student tickets

number of adult tickets was 120 less than twice student
a=-120+2s

total was 840

840=a+s
subsitute -120+2s for a
840=-120+2s+s
840=-120+3s
add 120 to both sides
960=3s
divide both sides by 3
320=s

sub back
a=-120+2s
a=-120+2(320)
a=-120+640
a=520

520 adult tickets
320 student tickets