Answer :
Let n be Martin's sister's age. Then Martin is n-6. So:
n+n-6≤22
2n≤28
n≤14
n-6≤8
The oldest Martin's sister can be is 14.
n+n-6≤22
2n≤28
n≤14
n-6≤8
The oldest Martin's sister can be is 14.
sisters age = x
martins age = x-6
equation: x +(x-6) <=22
2x -6 <=22
2x<=28
x<= 28/2
x<= 14