Em um triangulo abc, a medida do angulo bac excede a medida de abc em 10°,e a medida do amgulo acb, adicionada de 30°,é igual ao dobro da medida de bac. quais são as medidas dos angulos deste triangulo?

the question in English is

In a triangle ABC, the measure of the BAC angle exceeds the ABC measure by 10 °, and the measure of the ACB angle, added by 30 °, is equal to twice the BAC measure. What are the measures of the angles of this triangle?

Let 
A=m ∠BAC
B=m∠ABC
C=m∠ACB

we know that
A+B+C=180> equation 1
A=B+10> B=A-10> equation 2
C+30=2A> C=2A-30> equation 3

substitute equation 2 and equation 3 in equation 1
A+[A-10]+2A-30]=180> 4A=180+40> A=220/4> A=55°
B=A-10> B=55-10> B=45°
C=2A-30> C=2*55-30> C=80°

the answer is
m ∠BAC is 55°
m∠ABC is 45°
m∠ACB is 80°

the answer in Portuguese

Deixei
A=m ∠BAC
B=m∠ABC
C=m∠ACB

nós sabemos isso
A+B+C=180> equação 1
A=B+10> B=A-10> equação 2
C+30=2A> C=2A-30> equação 3

substitute equação 2 e equação 3 dentro equação 1
A+[A-10]+2A-30]=180> 4A=180+40> A=220/4> A=55°
B=A-10> B=55-10> B=45°
C=2A-30> C=2*55-30> C=80°

a resposta é
m ∠BAC is 55°
m∠ABC is 45°
m∠ACB is 80°

Ithink you answer is c