6k+10.5=3k+12
-10.5 -10.5
6k=3k+1.5
-3k -3k
3k=1.5
Subtract original amount from new amount:
84 - 39 = 45
He bought 45 books.
Answer:
A
Step-by-step explanation:
x² - 4x - 5 = 0
x² - 5x + x - 5 = 0
x(x - 5) + (x -5) = 0
(x - 5)(x + 1) = 0
x - 5 = 0 ; x + 1 = 0
x = 5 ; x = -1
