Question 16031
Let the cost of a taco = $t
and the cost of an enchiladas = $e

Now the cost of 2tacos and 3 enchiladas = 2t+3e = $8            (1)
The cost of 3 tacos and 6 enchiladas = 3t+6e = $15.15           (2)

Multiply (1) with 3 and (2) with 2

6t+9e = 24                   (3)
6t+12e = 30.30               (4)

Subtract (3) from (4)

6t+12e-(6t+9e) = 30.30  -24

3e = 6.30
Dividing by 3 throughout
e = $2.10
Substituting in any equation we get  t = $0.85 

Do let me know if I wasnt clear enough anywhere