#1
2a+3a=5a
7x-15x=-8x
-17b-3b=-20b
-2,1y+7y=4,9y
-2,5x+x=-1,5x
-a-0,8a=-1,8a
1/3x-2x=-1 2/3x
1/2a+1/5a=0,7a
5/6b-b=-1/6b
#2
8b+12b-21b+b=0
-13c+12c+40c-18c=21c
10a-a-b+7b=9a+6b
-15c-15a+8a+4c=-11c-7a
0,3x+1,6y-0,3x-0,4y=1,2y
-p-p-p-3p-p-p=-8p
4,14a+8,73a+5,8a-a=17,63a
5-a+4a-b-6a=-3a-b+5
1,2c+1-0,6y-0,8-0,2c=c-0,6y+0,2
#3
c+(a+b)=c+a+b
c-(a-b)=c-a+b
(a-b)-(c-d)=a-b-c+d
(a-b)+(c-d)=a-b+c-d
c-(a+b)=c-a-b
-c-(-a+b)=-c+a-b
x-(a-b)+(c-d)=x-a+b+c-d
10-(a-b)-(c+d)=10-a+b-c-d
#4
3b+(5a-7b)=-4b+5a
-3q-(8p-3q)=-3q-8p+3q=-8p
(2+3a)+(7a-2)=10a
-(11a+b)-(12a-3b)=-11a-b-12a+3b=-23a+2b
a+(a-10)-(12+a)=a+a-10-12-a=a-22
(6x-8)-5x-(4-9x)=6x-8-5x-4+9x=10x-12