Which resulted from the use of new weapons and methods of warfare during world war i? fighting caused very little damage to infrastructure. more people were killed than in any previous war. hand-to-hand combat disappeared from the battlefield. the war lasted only two years?

More people were killed than in any previous war.

Explanation:

The second half of the nineteenth century had witnessed a profound transformation of the basic weapon of the infantryman: the rifle. Of the load by the mouth, which forced the soldier to stand, he went to the backload, which allowed to load lying down. From the waxed paper cartridge, the compact metallic cartridge was reached; from the round bullet, to the pointed bullet. To this the bolt, the percussion by needle and the cordite, the gunpowder without smoke added, that, therefore, did not give away to the handle. The principles of portable weapons of the twentieth century were served.

The need to have a weapon with greater firepower in the attacks forced the evolution of the machine gun. This is how the light machine guns emerged, in the case of the American BAR of 1917, or the submachine guns (lighter than a rifle), such as the German Bergmann of the following year, the MP18.

One of the main problems of the infantry in the trench warfare was overcoming the dense wire fences parallel to the enemy lines, which could occupy a surface of up to 30 meters in width. British Colonel Ernest Swinton was struck by an idea when he saw a tractor pulling a cannon: maybe he could crush the barbed wire and carry the cannon to shoot. Churchill became a defender of the new weapon, which would be built in secret. The first specimens were packed as "tanks" of water, hence the name.

the perimeter of a triangle is 69 cm. side a is 5 cm shorter than side b. side c is twice as long as side a. find the length of each side. i need to know how to do it in 2 equations.  

equations:

a = b-5

c = 2a

a + b + c = 69

it granted civil rights to african americans.