parallel and perpendicular lines, in this situation the question in parallel [x-4y=12] [8,-4]

i just need help understanding why -x+12 over 4 equals to 1/4. the whole equation equals to y=1/4x-3 ​

parallel and perpendicular lines in this situation the question in parallel x4y12 84 i just need help understanding why x12 over 4 equals to 14 the whole equati class=