#3
a+3a+(a-10)=a+3a+a-10=5a-10
#7
a-(b+c)=(a-b)-c
#1
-4x*2y*(-3z)=-8xy*(-3z)=24xyz
-0,02a*50b=-ab
8xy*3xz=24xyz
#2
8c-4c-5c=4x-5c=-c
-2m+3n-8m-n+4m=-6m+2n
#4
11n-(7n-1)-6n+7=11n-7n+1-6n+7=-2n+8
n-(-6)
-2*(-6)+8=12+8=20
#5
-4(a-2c)+(4a-9c)=-4a+8c+4a-9c=-c
#6
7x+(2-(3x-2))=7x+(2-3x+2)=7x+2-3x+2=4x+4