Fair four sided die is rolled twice, what is the possibility of the sum to be 4 or less? A fair four sided die is rolled twice, what is the possibility of the sum of the 2 die rolls to be 4 or less?
could you please explain in detail

Record the result of the tossing as an ordered pair $(a,b)$, where $a$ and $b$ are integers between $1$ and $4$. Here the first coordinate records the result of the first toss, and the second coordinate records the result of the second toss.
(a) Let the number of such ordered pairs be $N$.  What is the value of $N$? 
There is a fast way of finding $N$. But one can do it slowly, by listing and counting. Here is a start: $(1,1)$, $(1,2)$, $(1,3)$, $(1,4)$.
(b) All these ordered pairs are equally likely.  How many ordered pairs give you a sum of $4$ or less? List and count them carefully. Let the number be $S$.
(c) Your probability is $\dfrac{S}{N}$.
