Question

find all values of x in (o, Pi) that satify the given equation
cos x/3=1/2

Answer 1

1.5

Answer 2

cos(pi/3) = 1/2
cos(5pi/3) = 1/2

so, x = pi or 5pi

Answer 3

oops only in [0,pi], so x=pi

However, you gave the interval as (0,pi), which excludes pi, so no solution.