A toy store marks down every toy by \[15\% \] in January. How much does a toy cost during January, using \[p\] for the price in December?

Hint: In this question, we are given the price of toys in December. We are asked to find the cost of toys in January after there is a discount of \[15\% \] . For this, we need to use the formula to determine the sales price after the discount and as a result we will get the price of toys in January in terms of the price of toys in December that is \[p\] .
Formula used:
 \[s = p(1 - d)\] , where, \[s\] is the sales price of the month when the discount is applied, \[p\] is the price of the previous month after which the discount is applied and \[d\] is the discount.

Complete step by step solution:
We are given the price of the December for the toys is \[p\] .
The toy store marks down every toy by \[15\% \] in January, therefore we will take $d = \dfrac{{15}}{{100}}$.
We need to find the cost of the toy in the month January which will be the sales price of January \[s\] .
Now, we will apply the formula for the sales price and then put these values in that formula.
 \[
  s = p(1 - d) \\
   \Rightarrow s = p\left( {1 - \dfrac{{15}}{{100}}} \right) = p\left( {1 - 0.15} \right) = 0.85p \;
 \]
Thus, the cost of the toy \[0.85p\] in the month of January after applying the discount, considering that \[p\] is the price of the toy in the month of December.

Note: In solving this type of question, we need to be careful while putting the value of the discount. We know that percentage means out of hundred. This means that we cannot put 15 as the value of discount in this problem. Instead, we need to put its value as $\dfrac{{15}}{{100}}$.