1) (х+y) - (y-z) - (z+2,9)= x+y-y+z-z+2,9=
x+2.9
2) (a+8)-(a+b)+(b-c)= a+8-a-b+b-c=8-c
3) (7-m)+(m+n)-(n-k)=7-m+m+n-n+k=k
4) (x-n) +(m-5)-(m-n)=x-n+m-5-m+n= x-5
1) (х+y) - (y-z) - (z+2,9)= x+y-y+z-z+2,9=
x+2.9
2) (a+8)-(a+b)+(b-c)= a+8-a-b+b-c=8-c
3) (7-m)+(m+n)-(n-k)=7-m+m+n-n+k=k
4) (x-n) +(m-5)-(m-n)=x-n+m-5-m+n= x-5