Enumerable Exercises

Write a method, #words_with_a, that accepts an array of strings as an argument. It should return the number of strings that have an 'a' in them.

 words_with_a(["enumerables", "are", "cake!"]) == 3
 words_with_a(["this", "is", "a", "string"]) == 1
 words_with_a(["ruby"]) == 0

Write a method, #odds, that accepts an array of integers as an argument. It should return an array containing only the odd numbers.
```
 odds([1,2,3,4,5,6]) == [1,3,5]
 odds([2,4,6]) == []
```
Write a method, #triple, that accepts an array of integers as an argument. It should return a new array with every element tripled.
```
 triple([1,2,3,4,5,6]) == [3,6,9,12,15,18]
```
Write a method, #odd_value_and_position, that accepts an array of integers as an argument. It should return a new array of all the elements whose value and position (index) in the original array are odd.
```
 odd_value_and_position([0,1,2,3,4,5]) == [1,3,5]
 odd_value_and_position([1,2,3,4,5]) == []
```

Exercises