Answer:
The triangle is not acute because 2² + 4² < 5².
Step-by-step explanation:
Answer: m = 10
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I believe it is A and D. All you have to do is add them all together and if both sides are the same then its a correct answer.
1. Given (12+3)x, we can sum the numbers in the parenthesis to get 15x
2. Given 12x+3x, we can factor x to get (12+3)x and get the same as 1.
3. Given (12+3x)x, we have to distribute the x and we have 
4. This expression is already simplified.