624/12 = 52
He will fill 52 boxes
(0 + a + b) / 3 = 2a
=> 0 + a + b = 6a
=> a + b = 6a
=> b = 5a
Okay, here we have this:
Considering the provided information, we are going to identify wich equation applies, so we obtain the following:

Where x represents the uknown number. Then finally we obtain that the correct equation is the third one.
Now, let's find the missing number solving the equation:

Finally we obtain that the number is equal to 19.
The price of movie after a year would be
7.50+

= 7.7625$
Greetings from Brasil...
Follow the reasoning.
288 ÷ 2 = 144
and 144 its a perfect square (144 = 12²)
It is visible that if we multiply 288 by 1/2, we will obtain a perfect square, but we will do this via a simple equation
288 · X = 144
X = 144 ÷ 288
X = 0,5 ⇔ X = 1/2