A = 15 ; b = ; c = 17

16

Step-by-step explanation:

b=16

Following the pattern, we can assume that each term adds by 1. So 15+1 = 16.

This is the concept algebra.
Volume of of paint that is required to paint  large shipping crate is a liters.
suppose the volume of this crate is x cubic units.
The volume of the next crate to be painted will be 2x cubic units.
Hence the amount of paint required to paint the crate will be:
(volume of bigger crate)/(volume of smaller crate)×(volume of liters required to paint the first crate)
=(2x)/(x)×a
=2a liters
To paint the new crate 2a liters of oil is needed.