Answer: 5
Step-by-step explanation:
Arimethic progression
An=a1+(n-1)d
An= nth term
A1= first term
N= nth position
D= common difference
For the 4th term=16
A4=a1+(n-1)d
16=a1+(4-1)d
16=a1+3d......equation 1
For the 7th term=31
A7=a1+(n-1)d
31=a1+(7-1)d
31=a1+6d.........equation 2
Subtract equation 1 from 2
31=a1+6d
16=a1+3d
15=3d
D=15/3
D=5
Common difference is 5
