Question 988961
J=Jack's age; M=Marin's age=J+3; R=Rob's age=J+7
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J+M+R=25
J+(J+3)+(J+7)=25
3J+10=25
3J=15
J=5 ANSWER 1: Jack is 5 years old.
M=J+3=5+3=8 ANSWER 2: Martin is 8 years old.
R=J+7=5+7=12 ANSWER 3: Rob is 12 years old.
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CHECK:
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J+M+R=25
5+8+12=25
25=25