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