Explanation:
1. -10b+b=-9
It is like you are doing this:
-10+1=-9
5. 5k+7k=12k
5+7=12
3. 1+5v+v= 1+6v
Like: 5+1
2.-x-3x=-4x
Like:-3-1=4 (both are negative numbers and you just add the second one)
4.-7n-7-8+10n=3n-15
You are doing this with n:
10-7=3 and this with numbers:
-7-8=-15 (both negative again)
6.a-2+1+4a= 5a-1
Like this: 4+1=5 and -2+1=-1
7. 8(x+10)= 8*x+8*10= 8x +80
8. 8(1+6p)= 8*1+8*6p= 8+48p
9.-5(-7+7n)= 35-35n ( when you * negative and positive numbers you get negative result and when you * negative and negative numbers you get positive result)
10.-(9m+7)= -9m-7 ( when you have - before () every number changes its sign).
Sorry for messy writing... Hope this helps.