You and a friend go to a mexican restaurant. you order 2 tacos and 3 enchiladas and your friend orders 3 tacos and 5 enchiladas. one bill was $7.80 plus tax and the other bill was $12.70 plus tax. how much was each taco and each enchilada?

For this case, the first thing we must do is define variables.
 We have then:
 x: cost of tacos
 y: cost of enchiladas.
 We write the system of equations:
 2x + 3y = 7.80
 3x + 5y = 12.70
 Solving the system we have:
 x = 0.9 $
 y = 2 $
 
 each taco and each enchilada was:
 x = 0.9 $
 y = 2 $

The answer that i got was 8/3