For example:

Left ☆☆☆☆

Right? ☆ ☆ ☆ ☆

4+5=9

5+4=9

9-5=4

9-4=5

Matters needing attention in mathematical formula are as follows:

1. Write the first addend on the top line first. If the two addends are different, write the number with more digits first.

2. Write the second addend on the next line. If the two addends are different, write the number with fewer digits.

Write "+"before the second number.

4. The sign "=" in the formula is indicated by a horizontal line and written below the second number.

5. Write the calculation results of two numbers below the horizontal line and align them with the numbers above.