Question 289102
Since you are dealing with squared numbers, you can not simply divide 80 by 2
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Set-Up:
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Let Molly's age = A
Let Anita's age = B
Equation 1: {{{A = 2B}}}
Equation 2: {{{A^2 + B^2 = 80}}}
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Solution:
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Substitute the 2B from equation 1 into equation 2 for A
Equation 2: {{{A^2 + B^2 = 80}}}
{{{(2B)^2 + B^2 = 80}}} Rewrite the equation
{{{(2B * 2B) + (B * B) = 80}}} Simplify
{{{4B^2 + B^2 = 80}}} Simplify
{{{5B^2 = 80}}} Divide both sides by 5
{{{B^2 = 16}}} Take the square root of both sides
{{{highlight(B = 4)}}}

Now plug 4 into equation 1 for B
Equation 1: {{{A = 2B}}}
{{{A = 2*(4)}}}
{{{highlight(A = 8)}}}