Suppose a movie theater sold 200 adult tickets for a showing with a revenue of $980. if the adult tickers were $6.50 and the student tickets were $4.50, how many of each ticket were sold?

A- number of adult tickets
s- number of student tickets
a       +s=200       }* - 4,5 ⇒
a*6,5+s*4,5=980 

a*6,5  +    s*4,5=980 
a*( -4,5) - s*4,5= - 200*4,5= -900

6,5a-4,5a=980-900=80
2a=80
a=80:2
a=40

s=200-40
s=160