Questions

A - A - A = 20
B - B - B = 15
C - C - C = 25

A = -20
B = -15
C = -25

=> A + B + C = (-20)+(-15)+(-25) = -20 - 15 - 25 = -60.

• International Workers' Day, also known as Labour Day in some countries, is a celebration of labourers and the working classes that is promoted by the international labour movement, socialists, communists or anarchists. 
• It occurs every year on May Day which is May 1st. It is the day to pay tribute to the Labourers. Without them nothing will complete. 
• In India, the first Labour Day, or May Day, was celebrated in 1923 in Chennai.

Adding the corresponding numbers in first and last figures gives the corresponding number in the middle figure.

i.e, 4 + 3 = 7

13 + 2 = 15

2 + 4 = 6

9 + 1 = 10

The one word substitute for "a person who is always dissatisfied" is malcontent.