Answer:
Let's Jiri's age be "J" and Pamela's age be "P".
P = 11 + J (Pamela is 11 years older than Jiri) ... equation 1
P + J = 35 (the sum of their ages is 35) ... equation 2
Put equation 1 into equation 2:
(11+J) + J = 35
11 + 2J = 35
2J = 35 - 11
2J = 24
J = 24/2
J = 12
Therefore,Jiri's age is 12.
