Don't understand

3 (2y+5)

21 or 6+15

Step-by-step explanation:

First: You'll have to multiple the outside number by both of inside numbers

(Example) : Multiply 3 by 2 getting the answer of 6, and multiply 3 by 5 getting the answer of 15. Then you'll be left with 6+15

Second: You'll have to add both of the answers you get after multiplying both problems

(Example) : You'll add 6 and 15 getting 21

What you would have to do is distribute your three to each number in the parentheses using multiplication so your answer would be 6y+15