Respuesta :

Answer:

8 minutes.

Step-by-step explanation:

We work in fractions of the wall they can paint in 1 minute, so

1/12 + 1/24 = 1/x  where x is the time it takes when working together.

Multiplying through by 24x:

2x + 1x = 24

3x = 24

x = 8 minutes.