in a quadrilateral ABCD ab is equal to BC if ab is equal to 6 CM CD is equal to 7 cm and ac is equal to 8 cm find perimeter of quadrilateral

Dear student, 
the diagram according to given information is
Without finding AD we can't find perimeter of quadrilateral and no information is provided to find AD. So either some data is missing in the question or the data provided is wrong. Kindly recheck your question and send again. So that we can provide you with some meaningful help. 
Regards
​​​​​