State if the three numbers can be the measures of the ustedes of a triangle.
12, 18, 9
Remember that
The triangle inequality theorem, states that
The sum of the lengths of any two sides of a triangle is greater than the length of the third side.
so
12+9 > 18
21 > 18 -----> is true
You only need to see that the two smaller sides are greater than the largest side
therefore
the answer is
Yes, the three numbers can be the measures of the ustedes of a triangle