Question 151590
Jessie is four years older than Lea. Eight years ago, he was twice as old as Lea. Find their present ages. Solve using two variables.
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Let J = Jessie's present age
and L = Lea's present age
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Since we have two unknowns, we'll need two equations.
From, "Jessie is four years older than Lea." we get equation 1:
J = L+4
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And from, "Eight years ago, he was twice as old as Lea." we get equation 2:
J-8 = 2(L-8)
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Using the definition of "J" from equation 1:
J = L+4
Substitute it into equation 2:
J-8 = 2L
(L+4)-8 = 2(L-8)
L+4-8 = 2L-16
L-4 = 2L-16
12 years = L (Lea's present age)
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Plug the above into equation 1 and solve for J:
J = L+4
J = 12+4
J = 16 years (Jessie's present age)