3+5=5+3
13=10+3
8-4=3-2
x + 5 = 5 + x
5+k = 5.k
7y + 4 = 4y + 7
4.(a+2) = 2a +2a + 4 + 4
x = 5 ise 5.x = 10
9m + m = 10m
90 = 10 + 80
