Jacob riis, upton sinclair, ida tarbell, and lincoln steffens were all:

Muckrakers, is the right answer.

Explanation:

The term muckrakers throughout the Progressive Era was used to refer those journalists who wanted to make some administrative reforms in the United States. these journalists presented authorized organisations and administrators as corrupt. Most of the muckrakers penned nonfiction, but fictional exposés usually had a significant influence too.

Upton Sinclair, Jacob Riis, Ida Tarbell, and Lincoln Steffens, were some of the prominent muckrakers of the time.

143.17

13.96 times 20.6 equals to 286.34, which is the area of 20 of those triangles, then you divide it by 2 and get 143.17

The formula of the area of a triangle is multiplying its sides and dividing by 2