The answer to the first one is y = 4.5x. This is because the number of teaspoons required to make the total amount of pudding is found by taking the number of servings your trying to make and multiplying the number needed to make each serving (or 4.5).
The answer to the second one is 4x - 5. Because x is Amy's age, and Ava is 4 times the age of Amy, minus five years, the problem is satisfied by this answer.
Hope this helps!
