You don’t necessarily have to do parentheses first. What matters is that the things inside the parentheses are a group that you can’t break apart. If you have 10÷2+3-2*(2+1) you can do the division first 5+3-2*(2+1) then the addition outside the parentheses 8-2*(2+1) It’s just that before you do the multiplication of the term outside the parentheses, you have to handle the parentheses group, so you get 8-2*3 -> 8-6 -> 2
You do parenthesis first and then multiplications and then sums, you did parenthesis, then sums, then multiplications, wich is wrong.
You don’t necessarily have to do parentheses first. What matters is that the things inside the parentheses are a group that you can’t break apart. If you have
10÷2+3-2*(2+1)you can do the division first5+3-2*(2+1)then the addition outside the parentheses8-2*(2+1)It’s just that before you do the multiplication of the term outside the parentheses, you have to handle the parentheses group, so you get8-2*3->8-6->2