a bag contains 7 read marbles and 5 black marble. You addd 60 marbles to the bag while keeping the ration of red marbles to blac
1 answer:
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Answer:
11 years old
Step-by-step explanation:
If four brothers have the average age 6, then the sum of their ages is
years.
Let x years be the age of sister. If four brothers and their sister have the average age 7, then
Multiply this equation by 5:
The sister is 11 years old.