Simplifying Algebra

Question 1:

x+x+x+x
4x

Question 2:

x+x+x+x+x
5x

Question 3:

2x+4x2x+3x
7x

Question 4:

4x+2xx+4x
9x

Question 5:

x+5y+4x+4y
5x+9y

Question 6:

5xzy+4xz4y
9xz-5y