Explain the distributive property so that a younger child could understand it

Basically, you take the number before the parenthesis ( <-- these things --> ) and multiply it by the numbers inside the parenthesis. 

For example:
3(2+5) +5 = 36

3 x 2 = 6

3 x 5 = 15

So now you have (6+15) +5 = 36

Then you solve (6+15) to get 31. 31 + 5 is 36. Sometimes drawing curved lines from the outside number to the ones inside the parenthesis can help, like a santa hat (It's nicknamed the santa hat property sometimes).