If one side of a parallelogram whose perimeter is42cm is 12cm , the measure of its adjacent side is.......................

it works just like a rectangle:

2(12+x) = 42

To find the measure of the adjacent side of the parallelogram, we need to understand the properties of a parallelogram.

A parallelogram is a quadrilateral with opposite sides that are parallel and equal in length. This means that the adjacent sides of a parallelogram are equal in length.

In this case, if one side of the parallelogram has a length of 12 cm, we can deduce that the adjacent side also has a length of 12 cm.

Therefore, the measure of the adjacent side of the parallelogram is 12 cm.