Question 939132
I am not sure that you copied the numbers in the problem over correctly because the answer comes out to odd prices but these are the steps that I used.


Let A = price of an adult.
Let C = price of a child.
Equation 1: {{{3A + C = 30}}}
Equation 2: {{{A + 4C = 22}}}
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Lets start by solving equation 1 for one of the variables. I picked C.
Equation 1: {{{3A + C = 30}}}
{{{C = 30 - 3A}}}
Now plug (30-3A) into equation 2 for C
Equation 2: {{{A + 4C = 22}}}
{{{A + 4*(30 - 3A) = 22}}}
Multiply the 4 through.
{{{A + 120 - 12A = 22}}}
Combine like terms.
{{{120 - 11A = 22}}}
Subtract 120 from both sides.
{{{-11A = -98}}}
Divide both sides by -11.
Notice that the negative signs cancel each other out.
{{{highlight(A = 8.91)}}} (Note that I rounded this number)}}}
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Using A = 8.91, solve for C
{{{C = 30 - 3A}}}
{{{C = 30 - 3*(8.91)}}}
{{{C = 30 - 26.73)}}}
{{{highlight_green(C = 3.27)}}}