Question

What volume of a 2.5 M NaOH solution is required to prepare 2.0 liters of a 0.75M NaOH?

Answer 1

Simple equality will do here as you have three things and require a fourth. 

(X L)(2.5 M NaOH) = (2.0 L)(0.75 M NaOH) 

2.5X = 1.5 

X = 0.60 Liters needed 

Answer 2

M1V1 = M2V2
2.5×V1 = 0.75×2
V1 = 1.5/2.5 = 3/5 = 0.6 Litres