Question 1035686
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Sara's age is 7 more than antonio's age.Two times Antonio's age plus 3 times sara's age is equal to 36. How old are they?
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s = a + 7,      (1)
2a + 3s = 36.   (2)

Substitute expression (1) for s into (2). You will get a single equation for a:

2a + 3*(a+7) = 36,

2a + 3a + 21 = 36,

5a = 36 - 21 = 15,

a = 3.

Antonio is 3 years old.
Sara's age is 3 + 7 = 10 years.
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