Question

Subtraindo -a+b=7 de 2a+b=1, quanto fica?

Answer 1

b = 7 +a

2a + 7 + a = 1
3a = 1 - 7
3a = -6
a = - 6/3
a = -2

b = 7 + a
b = 7 + (-2)
b = 7 - 2
b = 5

Resposta a = -2 e b = 5

Answer 2

$\boxed{ \left \{ {{-a+b=7} \atop {2a+b=1}} \right. } \\ b=7+a \\ \\ 2a+7+a=1 \\ 3a=1-7 \\ 3a=-6 \\ a= \frac{-6}{3} \\\boxed{a=-2} \\ \\ -a+b=7 \\ -(-2)+b=7 \\ 2+b=7 \\ b=7-2 \\ \boxed{b=5} \\ \\ \boxed{ \left \{ {{a=-2} \atop {b=5}} \right. }$