Question

57.0 mL of a 1.50 M solution is diluted to a total volume of 288 mL. A 144-mL portion of that solution is diluted by adding 117 mL of water. What is the final concentration? Assume the volumes are additive.

Answer 1

This is pretty easy,

(Original Concentration)(Volume Transfered/Diluted Volume) = New Concentration

SO we have,
1.50M*(57.0mL/288mL) = New concentration

Now you have the diluted concentration, just repeat this procedure to finish the question.

If you want to find the original concentration just flip the fraction volume fraction