Question

input output
1 5
2 8
4 14
8 ?

Answer 1

i/o
1 5 +4
2 8 +6
4 14 +10
8 ? +16
8+16=?
(Input is doubling.)

Answer 2

x=input
y=output

find the slope:
m=(y2-y1)/(x2-x1)
m=(8-5)/(2-1)=3

slope intercept form:
y=mx+b

y-y1=3(x-x1)
y-5=3(x-1)
y=3x+2

Output=3(input)+2