You have to get "X" by itself so you subtract 12, 7-12 is -5 so "X" = - 5
A librarian has 150 books to be placed on shelves with an equal number of books on each shelf. If k is the number of shelves to be used, then 150/k is the number of books on each shelf.
Example : lets say there are 10 shelves.....so k = 10
150/10 = 15 books on each shelf.
Answer:

Step-by-step explanation:
Given
P(A or B)= P(B)-P(A and B)
P(A)=1/3
P(A and B)=1/8
P(A or B)= 3/4
Required
Find P(B)
To find P(B), all we need to do is to substitute values of P(A or B) and P(A and B) in the given equation.
This goes thus;
P(A or B) = P(B) - P(A and B) becomes

Make P(B) the subject of formula

Take L.C.M

Add fractions

From the workings above, the value of P(B) using the given equation is 
Answer: (10 - 6i)/5
(x + yi) + (4(x + yi) + 6i) = 10
⇔ 5(x + yi) + 6i = 10
⇔ 5(x + yi) = 10 - 6i
⇔ x + yi = (10 - 6i)/5
Step-by-step explanation: