Answer:
1/5
Step-by-step explanation:
Well work can be defined as: 
where rate=amount of work that can be done in one unit of time
let a = rate of work A does in a day
let b = rate of work B does in a day
this means that:
where work=1 and it just means the entire job has been completed.
Since b can do it alone in 15 days, this means that: 
If we divide by 15 here, we get the equation: 
We can now use this definition to substitute it into the first equation we made.

Multiply the 10 and 1/15

subtract 2/3 from both sides

Now divide both sides by 10

Now multiply this by 6, since we a represents the amount of work that can be done in a day, we want to find how many parts of the work can be done by a in 6 days

Now divide both the numerator and denominator by 6
