Question 479964
The age of Betty's mother is 6 years more than four times Betty's age. The difference in their ages is 21 years. How old is Betty and her mother? 
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Equations:
m = 4b+6
m - b = 21
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Substitute  for "b" so you can solve for "m":
4b + 6 = b + 21
3b = 15
b = 5 yrs (Betty's age)
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Solve for "m":
m = b+21
m = 26 yrs (Mother's age)
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Cheers,
Stan H.