Before they reach high school, every United States math student learns the mnemonic: Please excuse my dear Aunt Sally (illustrated above with a picture of Jane Austen) for the order of evaluation of mathematical expressions.
The P is for parentheses, reminding the student that parentheses come first. Thus 3 x (1 + 2) is 9 and not 5.
The E is for exponents, reminding the student 1 + 2 squared is 5 and not 9.
The M and D are for multiplication and division, reminding the student that 2 + 1 x 3 is 5 and not 9.
At the lowest priority are A and S for addition and subtraction, reminding the student the evaluate these operations last.
The United States approach to teaching mathematics is to maximize the material taught each year and reteach that material year after year. However, in spite of teaching this lesson a half-dozen years in a row, or more, many students miss the point. This is clearly shown by the prevalence of order-of-evaluation puzzles that return over and over to social media.