Question 170711
these can be confusing at times. One must first find what is missing....we need Mary's ,Tom's, and Sally's ages, which we will call m,t,and s respectively.
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so we have 3 unknowns:so lets see if we can come up with 3 equations
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m=2t............eq 1
m=(1/3)s..........eq 2
m+t+s=99........eq 3
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lets rewrite eq 2 in terms of s and t by plugging in m's value from eq 1 into eq 2 (2t)=(1/3)s
multiply terms by 3---->6t=s---> now we have m(eq 1) and s(eq 2) in terms of t.
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so take m's value in eq 1 and s's re written value from eq 2 and plug them into eq 3
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2t+t+6t=99
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9t=99
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{{{highlight(t=11)}}}toms age
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from eq 1{{{highlight(m=2(11)=22)}}} mary's age
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from eq 2{{{highlight(s=6(11)=66)}}} sally's age