the complete question in the attached figure
we know that
[circumference]=2*pi*r
for r=10 in
[circumference]=2*pi*10-----> 62.8 in
if 360° (full circle) has a length of --------> 62.8 in
54°------------------------------> X
x=54*62.8/360-----> x=9.42 in
the answer is 9.42 in