In number system the relation "is factor of" is . concept of sets

μ₀ = 89

Step-by-step explanation:

A study has shown that  23 %  of all College textbook cost 95 $ or more,  then if the area under the bell shape curve is 23 % in the right tail, then

z(score ) = 0,74          ( 0,23 ≈  0,2296  from z table )

Then z(score) = ( x - μ₀ ) / σ

0,74  =  ( 95 -  μ₀ ) / 8,5

0,74*8,5 = 95 -  μ₀

6,29 - 95 = - μ₀

μ₀ = 88,71

μ₀ = 89