4b.
4b
b+b+b+c+c+c+c =3b+4c
b + b + b + c + c + c + c = 3b + 4c
a-b+a-b+2b+a = 4a
3b
b + a + b - a = 2b
Oh, isn't that a lovely question! When you add b plus b plus b plus b, you are actually adding 4 "b's" together. So, it's like having 4 beautiful little b's all snuggled up together, creating 4b. Just imagine those b's painting a happy little equation on the canvas of mathematics.
It is: b+b+b = 3b
b + b + b + 7 = 223b + 7 = 223b = 15b = 5
a+a+a+a+b+b - add the like terms =4a+2b 4a and 2b cannot be added because they are not like terms.
a+b+2+3=5+a+b