7a)

6 + k + 3 + 4k
= 9 + 5k

7b)

If k = 9,

Then total
= 9 + 9 x 5
= 9 x 6
= 54

Average = 54 ÷ 3 = 18


8a)

Notice the pattern repeats every 4 numbers : 4,0,1,2

So, group them into 1 set

626 ÷ 4 = 156 R 2

So for 626 numbers,

there are 156 sets of '4,0,1,2' and 2 standalone numbers that follow after it.

Since the pattern repeats, the last two numbers are 4,0.

So the 626th number is 0.


8b)


In each set, the sum of numbers is
4 + 0 + 1 + 2
= 7

There are 156 sets. So 156 x 7 = 1092

Looking at the pattern, the 627th number is 1 since the 626th is 0 which we already determined.

Sum of 627 numbers
Sum of 156 sets + next 3 numbers
= 1092 + 4 + 0 + 1
= 1097