What were three main styles of abstract they merge at the beginning of the 20th century?

Cubism.

Explanation:

This is the most influential style of the 20th century. It was developed in Paris by Picasso and Braque, beginning in 1907. The early mature phase of the style, called analytical Cubism, lasted from 1909 through 1911.

Abstract art was born at the beginning of the 20th century. At this time the artistic landscape was predominantly made up of fauvism, cubism and figurative expressionism.

Explanation:

the artist used rapid brushstrokes.