Suppose the number of pints of liquid is represented by p write an expression to find the number of fluid ounces

So p*1=p, right?

Well, since
1 pint=16 fluid ounces
divide both sides by 1 pint and get
(16 fluid ounces)/(1 pint)=1

Now that you know that (16 fluid ounces)/(1 pint)=1, you can solve the problem.

(P pints / 1) * (16 fluid ounces)/(1 pint)

Now, you can cancel out the "pints" from the numerator of the first term and the denominator of the second time to get

(P / 1) * (16 fluid ounces)/(1)

Which equals

16*P fluid ounces (this is the answer)