Questions

The logical answer for a puzzle is that the letter 'W'.

A rainbow is a spectrum of light that appears in the sky when sunlight is refracted through raindrops or other drops of moisture in the Earth's atmosphere. They have inspired much popular folklore, including the belief that a leprechaun can be found with a pot of gold at the end of a rainbow.

Now a days, printers we are using are called as laser printers. The speed of a laser printer is measured in PPM i.e, Pages Per Minute. 

Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics by repeatedly passing a laser beam back and forth over a negatively charged cylinder called a "drum" to define a differentially charged image.

Compared to inkjet printers which use ink for printing laser printers are more expensive as they use toner which lasts for long.

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.