Question

(700-a+200)-600=1000

Answer 1

700-a+200-600=1000
300-a=1000
-a=700
a=-700

Answer 2

(900-a)-600=1000. 900-a=1000+600, 900-a=1600, -a=1600-900, -a=700, a=700/(-1)= -700. Ответ: a= -700.