Respuesta :

Answer:

teo= 15 years old

richard= 27 years old

Step-by-step explanation:

richard=r

teo=t

r + t=42

t + 12= r

u can use substitution here  

(t+12) + t=42

2t + 12= 42

2t=30

t= 15

to find r, you just do 15 + 12= 27

to check you can do 27 + 15= 42