Question 388138
First problem,
{{{A+B=20}}}
{{{B=5+A}}}
Substituting,
{{{A+5+A=20}}}
{{{2A=15}}}
{{{highlight(A=15/2)}}}
Then,
{{{B=5+15/2}}}
{{{B=10/2+15/2}}}
{{{highlight(B=25/2)}}}
A is 7.5 feet long, B is 12.5 feet long.
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Second problem,
{{{A+B=20}}}
{{{8+B=20}}}
{{{highlight_green(B=12)}}}
A is 8 feet long, B is 12 feet long.