8дм 1см + 9 = 8дм + 3м 2дм

8дм 1см + 9 = 8дм + 300см

8дм + 100см + 9 = 8дм + 300см

8дм + 109см = 8дм + 300см

Since the two sides are equal, the statement is true.

9дм - 5см = 5м - 9дм

90см - 5см = 500см - 90см

85см = 410см

Since the two sides are not equal, the statement is false.

5м - 9дм = 500см - 90см

500см - 90см = 410см

5м = 410см

Since the two sides are not equal, the statement is false.