Answer:9
Explanation:
1st triangle is similar to the second one as the angles of both of the triangles are the same..
So we know the ratio of the similar lines will be constant.it means,
XY/PQ=XZ/PR=YZ/QR
So,Xy/PQ=XZ/PR
21/7=27/x
X=(27×7)/21
X=9
Thats the value of pr..