Questions

The Great wall is a mighty monument to the building skill of ancient China. This wall, built of stone and earth to a height of 6 metres and extending over 2400 kilometres of hills and valleys, links the east coast with the mountains of the west right across northern China. The wall was wide enough for a carriage to go through.At intervals of every few hundred metres were located watch towers for warriors. Such a large study construction must have taken decades and an army of labourers to complete it. 

Let the given be resembled in letters like R, G & B.

Here given,

1) R + R + R = 30

=> 3R = 30 => R = 30/3 = 10

2) R + G + G = 18 => R + 2G = 18 => 10 + 2G = 18 => 2G = 8 => G = 4

3) G - B = 2 => B = G - 2 => B = 4 - 2 => B = 2

Hence, R + G + B = 10 + 4 + 2 => 16.