$ 450,000 worth of pencils is a LOT of pencils !
Markup 9 % = .09 450,000 (1.09) = $ 490500.
If he sold them all and got this much money, that is a HUGE profit because he spent only 3600 + 450,000
Profit = GROSS income - costs = 490500 - (450,000 + 3600) = $ 36,900.
SECOND question:
x = the number
2x = twice the number
-2x =two times the opposite of number
so: (2x) = 16 + (-2x)
2x = 16 -2x
4x = 16
x = 4