For every 4 of my wonderful nieces, I want to buy 5 Friendly cupcakes. And I have 12 wonderful nieces.

15 cupcakes

Step-by-step explanation:

I'm guessing you mean that you want to find out how many cupcakes you'll need to buy.

3< x< 5

step-by-step explanation:

|x - 4| < 1

there are two solutions, one positive and one negative.   remember to flip the inequality when taking the negative solution

x-4 < 1       x-4 > -1

add 4 to each side

x-4+4 < 1+4       x-4+4 > -1+4

x< 5                 x> 3

3< x< 5