Выражение 1) 7a-9b+(a+b) 2) (3m-7n-5p)+(2m+4n--3n-6p)

1) =7a -9b +a +b =8a -8b или =8(a -b)

2) =3m -7n -5p +2m +4n -3p -4m +3n +6p =m -2p

(3m+2m-4m) =m
(-7n+4n+3n) =0
(-5p-3p+6p) =(-8p+6p) = -2p

ответ: m -2p