Question

Pamela's age is two times Jiri's age. The sum of their ages is 81. What is Jiri's age?

Answer 1

p = 3j
p + j = 64
4j = 64
j = 16

Answer 2

let us say that
Pamela's age= P
Jiri's age=J
then P=2J
and P+J=81
u can put 2J instead of P in the second equation
2J+J=81
3J=81
J=27

Answer 3

j= jiri
p=2j
j+2j=81
3j=81
j=27
jiri is 27 and pamela is 54