A) 17 – (2 + X) = 3 ; B) (6 + X) – (17 – 21) = -25 ; C) -10 – (31 – X) = 40

Bài 7.7.Tìm x, biết:a) 17 – (2 + x) = 3 ; b) (6 + x) – (17 – 21) = -25 ; c) -10 – (31 – x) = 40.