Rule

The Use of Numbers in Essays and Reports

Numbers should be expressed in words unless they are:
Greater than or equal to 10, ages, times of day, dates, percentages, ratios, fractions or decimals, exact sums of money, scores and points on a measurement scale, page numbers, series of four or more items, numbers grouped for comparison if any is greater than or equal to ten, sample or population sizes.
If a sentence begins with a number, then that number should be expressed in words.
When writing numbers in words, you must use hyphens when the number is made up of more than one word.

How to correct use contraction?

Add 's to the end of the word if the word is in singular form ,even if the word ends in the letter s
Add 's to the plural form of a word if the word does not end in the letter s
Add ' ( an apostrophe) to the end of a plural noun that ends in the letter s
To attribute joint ownership, follow the above apostrophe rules, but add an apostrophe only to the last noun.
(Thomas and Blackmun's experiment)
Worked together to development the experiment
If you want to show possession without joint ownership, each noun needs to be given an apostrophe according to the above rules.
（Thomas's anexpermientsd Blackmun's ）
Conducted different experiments separately
Do Not Add an apostrophe to the end of possessive pronouns.