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Step by step explanation This is how I got the answer to your question and I gave you the solution I hope this helps you out
Answer:
two of the sides are 21 m long and one of the sides is 28 m long
X= 12
Add three on both sides to get rid of it
9+3 and -3 + 3 the three is negative because you drop the minus sign down
This cancels out the three and 9+3 is 12 so X=12
Answer:

Step-by-step explanation:

Lets add +5 in both the sides.


Now lets divide 12 on both the sides.


Answer:
410.625
Step-by-step explanation: