Question 699126
Equation 1: {{{A + B = 30}}}
Equation 2:{{{A/B = B}}}
Solve equation 2 for A by multiplying both sides by B
{{{A = B^2}}}
Now plug B^2 into equation 1 for A
Equation 1: {{{A + B = 30}}}
{{{(B^2) + B = 30}}}
Subtract 30 from both sides to set the equation equal to zero
{{{B^2 + B - 30 = 0}}}
Now you can use the quadratic equation
*[invoke quadratic "B", 1, 1, -30]
Note that B can equal 5 or -6. 
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Plug 5 into equation 1 for B
Equation 1: {{{A + B = 30}}}
{{{A + (5) = 30}}}
Subtract 5 from both sides
{{{highlight(A = 25)}}}
Check your answer:
5 + 25 = 30 That checks
25 / 5 = 5 That checks
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Plug -6 into equation 1 for B
Equation 1: {{{A + B = 30}}}
{{{A + (-6) = 30}}}
Add 6 to both sides
{{{highlight(A = 36)}}}
Check your answer:
-6 + 36 = 30 That checks
36 / -6 = -6 That checks
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So for this problem you have two answers: 5 & 25, or -6 and 36