Nikola and Ilia finished their work for 10 days. Nikola finished the work for 15 days alone. For how much time did Ilia finished the work al

Thanks Alan,

I am going to play with this one as well because I  need the practice.

Nikola does   $$\frac{1}{15}$$   of a unit of work in a day.

Nikola and llia together do  $$\frac{1}{10}$$  of a unit of work in a day

so llia must do  $$\frac{1}{10}-\frac{1}{15} = \frac{3}{30}-\frac{2}{30}= \frac{1}{30}$$ 

So by herself llia would take 30 days to complete the task

this question is kind of confusing me ...was their any other info given?

Rosala, I think this question could be rephrased as follows:

Nikola can complete N units of work on her own in 15 days.

Nikola and Ilia together can complete N units of work in 10 days.

In how many days could Ilia complete N units of work on her own?

Note that Nikola works at a rate of N/15 units of work per day.

Assume Ilia works at a rate of N/T units of work a day.  The idea is to find the value of T.

(N is unknown of course.)

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