Homework Help: Math

Posted by Anjanique on Tuesday, February 8, 2011 at 8:46am.

Sally's age is 12 years plus half her age. How old is she?

Billy is twice as ld as Sally was when billy was as old as Sally is now. And the total ages is 28 how old are they?

Math - drwls, Tuesday, February 8, 2011 at 9:08am
Let Sally's age be S.

S = 12 + (S/2)
S/2 = 12
S = 24
=============================
(new question; different age for Sally, S)

Let Billy's age(now) be B; Sally's age (now) = S. Billy is older by B-S years

B + S = 28

B = 2*[S - (B-S)] = 4S -2B
3B -4S = 0
4B + 4S = 112
7B = 112
B = 16
S = 12

When Billy was 12, Sally was 8; he is 16 now. It checks

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