Question

If an angle of parallelogram is three fifth of its adjacent angle

Answer 1

Let the angle be x°

Adjacent angles of parallelograms are supplementary.

So, adjacent angle's measure will be 180°- x°

According to question

$x = \frac{3}{5} (180 - x) \\ 5x = 540 - 3x \\ 8x = 540 \\ x = \frac{540}{8} = 67.5$

Therefore required angle's measure is 67.5°

Hope this clears your doubt