Answer:
5040
Step-by-step explanation:
The given series is :
24 + 48 + 72 + 96 +...+ 480
The first term, a= 24
Common difference, d = 24
The last term, 
Let there are n terms in the AP.
So,

There are 20 terms in the series. The sum of 20 terms is :

So, the sum of the given arithmetic series is equal to 5040.
Short side length = x
Medium side = x + 7
Long side = 5x
Total 49, so
x + x + 7 + 5x = 49
If you combine like terms:
7x + 7 = 49
Subtract 7 from both sides
7x = 42
Divide both sides by 7
x = 6 inches.
It's B, remember when you have _ ( referring to =) you have straight line, but when it's just < or > you have dotted line