Give two examples that show how using parentheses can change the order i. witch operations are performed in an expression

The order of arithmetic operations is given by the acronym PEMDAS, which means
Parentheses,
Exponents,
Multiplication,
Division,
Addition,
Subtraction.

These two examples illustrate how the use of parentheses can change the order.

Example 1:
5+7/3x4-2/5 has an answer of 13.933.

Use PEMDAS to obtain
5+(7/3)x4-(2/5)
= 5+(2.3333x4)-0.4
= 5+9.3333-0.4
= 14.3333-0.4
= 13.933

If we apply the parentheses: (5+7)/3x4-2/5
The result is
(12/3)x4-(2/5)
= (4x4)-0.4
= 16-0.4
= 15.06
which is a different answer.

Example 2:
8/3²x5+4 has the answer 8.444

Use PEMDAS to obtain
8/(3²)x5+4
= (8/9)x5+4
= (0.8889x5)+4
= 4.4444+4
= 8.4444

If we apply the parentheses (8/3)²x5+4:
The result is
2.6667²x5+4
= 7.1113x5+4
= 35.5565+4
= 39.5565
which is a different answer.

9/12 is the answer because 3/4 times 3 each is 9/12