x+y+z=116 y=2x+4 z=y+3=2x+7 x+2x+4+2x+7=116 x=21 y=46 z=49
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$\small AB+CD+EF=116\,cm;$
quindi guardando il disegno:
$\small AB= 116-4AB-2×4-3$
$\small AB+4AB = 116-8-3$
$\small 5AB = 105$
$\small \dfrac{\cancel5AB}{\cancel5} = \dfrac{105}{5}$
$\small AB= 21$
per cui risulta:
$\small AB= 21\,cm;$
$\small CD= 2AB+4 = 2×21+4 = 42+4 = 46\,cm;$
$\small EF= 2AB+4+3 = 2×21+7 = 42+7 = 49\,cm.$