Aparticular experiment requires 13.5 µl hydrochloric acid solution. if 250 ml hydrochloric acid solution is available, how many times can the experiment be performed? about 18 about 18,500 about 18,500,000

This is a simple unit conversion problem.

1 mL= 1 x 10⁻³ L 
1 μL = 1 x 10⁻⁶ L

So, we can convert 250 mL and 13.5 μL into L as follows,
         250 mL = 250 x 10⁻³ L
         13.5 μL = 13.5 x 10⁻⁶ L

1 experiment requires 13.5 μL  of HCl.
Hence,
    the number of experiments = total volume / volume per experiment
                                                   = 250 x 10⁻³ L / 13.5 x 10⁻⁶ L
                                                   = 18518.518
                                                   = 18518
(number of experiments should be a whole number. Hence we have to choose 18518)

Hence, the number of experiments which can be performed is about 18500.

Because it was a dramatically big guy