Attached below is the problem that I worked out. And I checked my answer simply by plugging it in
The question is asking for the sector arc length WZ,which can be find through the sector formula:

Since both cz and wz are the radius, they have the same length
cz=wz=5 in.
In this case,
2丌(5)× 122°/360°
=10丌×61/180
=61/36 ×丌
≈5.32in.
Thus 5.32in. is the answer.
Hope it helps!
Ok, a=f/m
What we need to do is isolate the variable, m.
a=f/m
*m *m
a*m=f
m*a=f
/a /a
m=f/a
There's your answer.