fix(guide): restructure curriculum guide articles (#36501)

* fix: restructure certifications guide articles
* fix: added 3 dashes line before prob expl
* fix: added 3 dashes line before hints
* fix: added 3 dashes line before solutions

guide/english/certifications/coding-interview-prep/project-euler/problem-2-even-fibonacci-numbers/index.md

@@ -1,9 +1,10 @@
 ---
 title: Even Fibonacci Numbers
 ---
-## Problem 2: Even Fibonacci Numbers
+# Problem 2: Even Fibonacci Numbers
 
-### Method:
+---
+## Problem Explanation
 - A fibonacci sequence is a sequence where `fib(n) = fib(n-1) + fib(n-1)`.
 - In this challenge we have to sum all the even numbers upto `nth` term in the sequence.
 - Example for `fiboEvenSum(10)`:
@@ -13,34 +14,51 @@ title: Even Fibonacci Numbers
   + Sum of all even number in the above sequence is:
   2 + 8 + 34 = 44
 
-### Solution:
+#### Relevant Links
+- [Wikipedia](https://en.wikipedia.org/wiki/Fibonacci_number)
 
-#### Basic Solution - Iterative:
+
+---
+## Solutions
+
+<details><summary>Solution 1 (Click to Show/Hide)</summary>
+
+Iterative
 ```js
 function fiboEvenSum(n) {
-  let first = 1, second = 2, sum = 2, fibNum; // declaring and initializing variables
+  let first = 1,
+    second = 2,
+    sum = 2,
+    fibNum; // declaring and initializing variables
   if (n <= 1) return sum; // edge case
-  for (let i = 3; i <= n; i++){  // looping till n
-    fibNum = first + second;    // getting the ith fibonacci number
+  for (let i = 3; i <= n; i++) {
+    // looping till n
+    fibNum = first + second; // getting the ith fibonacci number
     first = second;
     second = fibNum;
-    if (fibNum%2 == 0) sum+=fibNum;  // If even add to the sum variable
+    if (fibNum % 2 == 0) sum += fibNum; // If even add to the sum variable
   }
   return sum;
 }
 ```
-#### Advanced Solution - Recursive:
+</details>
+
+<details><summary>Solution 2 (Click to Show/Hide)</summary>
+
+Recursive
 ```js
-// We use memoization technique to save ith fibonacci number to the fib array 
-function fiboEvenSum(n){
-  const fib = [1, 1, 2]; 
+// We use memoization technique to save ith fibonacci number to the fib array
+function fiboEvenSum(n) {
+  const fib = [1, 1, 2];
   let sumEven = fib[2];
-  function fibonacci(n){
-    if (n <= 1) return fib[n]; // base condition
-    else if (fib[n]) return fib[n]; // if the number exists in the array we cache it and return
+  function fibonacci(n) {
+    if (n <= 1) return fib[n];
+    // base condition
+    else if (fib[n]) return fib[n];
+    // if the number exists in the array we cache it and return
     else {
-      fib[n] = fibonacci(n-1) + fibonacci(n-2); // otherwise calculcate and save it to the array
-      if (fib[n]%2 == 0) sumEven+=fib[n];  //if the number is even, add it to the sumEven variable
+      fib[n] = fibonacci(n - 1) + fibonacci(n - 2); // otherwise calculcate and save it to the array
+      if (fib[n] % 2 == 0) sumEven += fib[n]; //if the number is even, add it to the sumEven variable
       return fib[n];
     }
   }
@@ -48,6 +66,6 @@ function fiboEvenSum(n){
   return sumEven;
 }
 ```
+</details>
+
 
-### References:
-- [Wikipedia](https://en.wikipedia.org/wiki/Fibonacci_number)