Question

Labor unions were first formed in the interest of protecting

Answer 1

Labor unions were first formed in the interest of protecting were created in the idea of helping workers with difficulties that fall under the category of work-related. (ex; low pay, long hours, etc). Although this became a problem because those said workers often had problems with their boss/bosses in the result that they joined a union.

Answer 2

Labor unions were created in order to help the workers with work-related difficulties such as low pay, unsafe or unsanitary working conditions, long hours, and other situations. Workers often had problems with their bosses as a result of membership in the unions.
Hope this helps.