Answer:
a) 4x
b)
[tex]8 \cdot \: 9y - 8 \cdot2[/tex]
and
8(9y-2)
Step-by-step explanation:
For part a) We want to simplify:
[tex]x + x + x + x[/tex]
This gives us
[tex]4x[/tex]
For part b), we factorize
[tex]72y - 16[/tex]
There is a common factor of 8
[tex]72y - 16 = 8 \times 9y - 8 \times 2[/tex]
This also equals:
[tex]72y - 16 = 8 (9y - 2)[/tex]