[Edit:}
Okay! So after you have 15+(21)÷3, you have to remember PEMDAS.
PEMDAS is the order in which you solve equations.
1. Parentheses: you solve everything in the parentheses first, all while following the rules of PEMDAS
2. Exponents: after you solve the things in the parentheses, you do the exponents.
3. Then you do Multiplication or Division, solving in the order from left to right.
4. After, you do Addition or Subtraction, solving in the order from left to right.
So using PEMDAS, we'll solve 15+(21)÷3.
We do division before addition, so 21/3 is 7.
Then you add 15 to 7 and get 22 as your final answer.
Hope this helps!
