The answer to this question is 10. The working out is shown in the image attached.
*** Sorry instead of writing 170 I wrote 270 for the big angle.. other than that it's correct
or another way to solve this is....
we know that a straight line is 180 degrees and the angle APD is 170 all we need to do is subtract 170 from 180 to get the answer of DPB
Hope this helped