Okie, it is not too hard.
Set these numbers a and b, notice a, b positive.
We have a+b=42.
You can see the next on my photo
Or you can use the formula of Cauchy
2 men and 3 women
3 men and 2 women
4 men and 1 women
5 men and 0 women
(Total of 4 ways)
1/8 of anything is just 1/8 * anything, so
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 $
Answer:
each taco and each enchilada was:
x = 0.9 $
y = 2 $