To determine the possible length of the third side of a triangle when the first two sides measure 10 and 12, we can use the triangle inequality theorem. This theorem states that for any triangle with sides of lengths \( a \), \( b \), and \( c \):
- \( a + b > c \)
- \( a + c > b \)
- \( b + c > a \)
Let the lengths of the two sides be \( a = 10 \) and \( b = 12 \). Let \( c \) be the length of the third side.
Using the triangle inequalities:
- \( 10 + 12 > c \) ⇒ \( c < 22 \)
- \( 10 + c > 12 \) ⇒ \( c > 2 \)
- \( 12 + c > 10 \) ⇒ \( c > -2 \) (this inequality is always true for positive \( c \))
From the first two inequalities, we find:
- \( 2 < c < 22 \)
Therefore, the length of the third side must be greater than 2 and less than 22. The only response you provided that falls within this range is 15.
So, the length of the third side of the triangle is 15.