Parentheses are preceded by a plus sign (that is, a+sign). Remove the brackets and keep the symbol unchanged.

There is a minus sign (that is, a minus sign) in brackets. Remove the brackets, remove the minus sign, and change the number inside.

For example:

78+(25+36)

=78+25+36 (without brackets, the items in it remain unchanged)

= 139

78-(25+36)

=78-25-36 (Remove the brackets and the minus sign, and the symbols inside will change, 25 will become -25, and +36 will become -36. )

= 17

You got it?

By the way, haven't you read the first grade yet?