Question 1023983
Ben is 12 years older than Lisa. 
The sum of their ages is 64. 
How old is Ben? 
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B = L + 12
B + L = 64
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Substitute for "B" and solve for "L"::
L + 12 + L = 64
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2L = 52
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L = 26 yrs (Lisa's age)
B = L+12 = 38 yrs (Ben's age)
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Cheers,
Stan H.