My niece out it’s been ages since i’ve done this

Ответ:

arturo698839

02.07.2020

the sum of the measures of triangle's angles is always 180°. if

$m\angle a= 2x^{\circ},\\ m\angle b= 3x^{\circ},\\ m\angle c= 4x^{\circ},$

then

$2x^{\circ}+3x^{\circ}+4x^{\circ}=180^{\circ}.$

solve this equation:

$9x^{\circ}=180^{\circ},\\ x=20^{\circ}.$

thus,

$m\angle a= 2x^{\circ}=40^{\circ},\\ \\ m\angle b= 3x^{\circ}=60^{\circ},\\ \\ m\angle c= 4x^{\circ}=80^{\circ}.$

answer: correct choice is b.

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