Answer:
7(3a + 5)
Step-by-step explanation:
Rewrite 21 as 7 · 3
Rewrite 35 as 7 · 5
Therefore,
⇒ 21a + 35 = 7 · 3a + 7 · 5
Factor out common term 7:
⇒ 7 · 3a + 7 · 5 = 7(3a + 5)
78, because you have to do the inverse operation so 80/2= 40 then 40-1= 39 and 39*3 = 78
Answer: Number of ways 
Step-by-step explanation:
When there is no replacement , we use combination to find the number of ways to choose things.
Number of ways to choose r things out of ( with out replacement) = 
The number of ways to choose 8 things = ![^8C_8=\dfrac{8!}{8!(8-8)!}=\dfrac{1}{0!}=1 [\because 0!=1]](https://tex.z-dn.net/?f=%5E8C_8%3D%5Cdfrac%7B8%21%7D%7B8%21%288-8%29%21%7D%3D%5Cdfrac%7B1%7D%7B0%21%7D%3D1%20%20%5B%5Cbecause%200%21%3D1%5D)
Hence, Number of ways 