Respuesta :

Interior angle add up to 360, so you add
(a+10) + (3a+10) + (5a-10) + (3a-10) = 12a

12a =360
a= 30
30+10=40
3(30)+10=100
5(30)-10=140
3(30)-10=80

You can double check they're correct by doing 40+100+140+80, which equals 360.
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