What is the common difference in the following arithmetic sequence ?

11

Step-by-step explanation:

The common difference of an arith. seq. is the distance between any two adjacent members of the sequence.

The difference (increase) between -1 and 10 is +11.  

as a check, determine whether adding 11 to y = 10 results in 21.  Yes, it does.

The common difference here is 11.

D

Step-by-step explanation:

edge

2/3

Step-by-step explanation:

Gradient = rise/run

rise = 80 - 60 = 20

run = 70 - 40 = 30

Gradient = 20/30 = 2/3