Let's try to find a relationhip between Y and X in the graph
0 - 95
1 - 85
2 - 90
Between these three points we see that (95 + 85) / 2 = 90
3 - 80
4 - 70
5 - 75
Between these three points we see that (80 + 70) / 2 = 75
Wese e that the difference betwen the value 2 and value 3 is : 90 - 80= 10
So, the sixth value will be 75 - 10 = 65
The seventh value is (75 + 65)/2 = 70
The seventh value will probably be 70