When spark plug cables aren't far enough apart, premature firing of adjacent spark plugs can happen. this is known as?

Speed is how fast an object moves a certain distance within a length of time. how is speed calculated? a) distance/time b) time/distance c) velocity/time d) distance x time

Why were most movies from the late 1890s until the early 1930s only filmed in black and white? there were only a few people who could afford the technology to produce color motion pictures back then. audiences did not want color motion pictures until later. the film used to make color motion pictures often overheated, which was a safety hazard, so it was generally not allowed. color films had to be hand-colored, frame by frame.

Whats three fourths of 15(this is supposed to be in math but i clicked too fast)