On the 21st day, he sprints 205 yards.
Is that what you meant for the problem
or do u want to know how many yards he sprinted total for the 21 days
If it is,
he sprinted a total of 3390 yards
Let the common multiple be x
3x : 2x
3x = 125
x = 125/3
So, B pays 2x = 2 × 125/3 = £250/3
