Answer:
14cm
Explanation:
To find the third side of a triangle when given the perimeter and the length of two of its sides, you can use the following formula:
Perimeter = side1 + side2 + side3
Given the perimeter of 42cm and two sides 16cm and 12cm
We can find the third side by subtracting the known sides from the perimeter:
side3 = Perimeter - side1 - side2
so,
side3 = 42 - 16 - 12 = 14cm
Therefore, the third side of the triangle is 14cm.