Respuesta :

Answer: Jiří is 5 years old.

Step by step:

Let x denote Jiří's age in years. Then Pamela's age is 3x. Their sum is x + 3x = 20. So we solve for x:

x + 3x = 20

4x = 20

x = 5

Jiří's age is 5 years

Pamelas age is 5 x 3 = 15, So Juri age is 5