Given:
Sides of triangles in the options.
To find:
Which could NOT be the lengths of the sides of a triangle.
Solution:
Condition for triangle:
Sum of two smaller sides of a triangle must be greater than the longest side.
In option A,

Sides 5 in, 5 in, 5 in are the lengths of the sides of a triangle.
In option B,

Sides 10 cm, 15 cm, 20 cm are the lengths of the sides of a triangle.
In option C,

Sides 3 in, 4 in, 5 in are the lengths of the sides of a triangle.
In option D,

Since, the sum of two smaller sides is less than the longest side, therefore the sides 8 ft, 15 ft, 5 ft are not the lengths of the sides of a triangle.
Therefore, the correct option is D.
Well the 2 in 8.524 would be 0.02 or 2 hundredths. Here's my explanation, the 8 is the whole number because it's before the decimal point, the 5 is the tenth or 0.5 and as you go further the number gets smaller so after the 5 is the 2 and that would be 2 hundredths or 0.02. So basically it's like going from tens, to hundreds, to thousands but only going in reverse order.
Answer: x = 10
Explanation: The bottom left angle is 90 degrees because of the symbol. ( Make sure you know this for future problems.) The whole triangle needs to add up to 180. This isn’t the right way to solve this kind of problem but I know how to solve it using this way and I know the at 10 is the right answer. The other two angles need to add up to 90 because 90 + 90 = 180. So basically I just substituted the same number into x until I added both outcomes and got 90. I hope you understand that cause I don’t really know how to explain it well. Let me try and show you.
3(x)+5 6(x)-5
Now you have to plug in the same number for x until both numbers add to ninety.
3(5)+5 6(5)-5.
( 5 isn’t the right number for x this is just an example. )
You end up with 20 for the first one, and 25 for the second one. 20 + 25 = 45 and 90 + 45 is only 135. So this means that 5 isn’t the right answer and you need to substitute a higher number in for x.
3(10)+5 6(10)-5
( This is the right setup. )
You end up with 35 for the first one and 55 for the second one after you distribute and solve. Now you have 35 and 55. 35 + 55 = 90 and 90 + 90 = 180. This is how you know that you are right. I hope this helps. :)