Chemistry
posted by Jessi .
How many milliliters of a 2000.0 mg/dl stock solution are needed to prepare 100.0 ml of a 150.0 mg/dl working solution?

Use the "dilution formula":
V1C1 = V2C2
V1, C1 = initial volume and concentration
V2, C2 = final volume and concentration
Your unknown is V1. Substitute the other which are given and solve for V1. 
Use the "dilution formula":
V1C1 = V2C2
V1, C1 = initial volume and concentration
V2, C2 = final volume and concentration
Your unknown is V1. Substitute the other which are given and solve for V1.