Question 879610
Write everything you can understand or are facts about the problem.


w for width
L for length
2w+2L=70, w=(40/100)L, w=(4/10)L, w=(2/5)L.


Identify the system of equations which describe well the problem:
{{{2w+2L=70}}} and {{{w=(2/5)L}}}.
The coefficients and constant term of the perimeter equation are even numbers, so division by 2 will give a simpler equation:
{{{w+L=35}}}.


You have various choices about solving the system, which can now be listed as:
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w+L=35 AND w=(2/5)L
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Solve for L and w.