Nick said that his sister is 4 times as old as his brother, and together their ages add to 20 comple

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Nick said that his sister is 4 times as old as his brother, and together their ages add to 20 complete this equation to find his brothers age

Let b be the brother's age and s be the sister's age. We're given two equations:

1. s =4b
2. b + s = 20

Plug (1) into (2):
b + 4b = 20

Type this equation into the search engine, and we get:
b = 4