Answer :

n = the number

0.5n - 9 = 4n + 5
(0.5n - 0.5n) - 9 = (4n - 0.5n) + 5
-9 = 3.5n + 5
(-9 - 5) = 3.5n + (5 - 5)
-14 = 3.5n
-14/3.5 = 3.5n/3.5
-4 = n

The number is -4.