we can use the following equation to calculate the concentration of diluted solution.
c1v1 = c2v2
where c1 is concentration and v1 is volume of stock solution, which is the more concentrated solution.
c2 is concentration and v2 is the volume of diluted solution.
substituting the values in the equation,
0.188 M x 25.0 mL = c2 x 150.0 mL
c2 = 0.0313 M
concentration of diluted solution is 0.0313 M