first you have to find the slope of the given points which is 3/4. to find slope you do change in y over chance in x. that equation is y2 - y1 over x2 - x1. when you plug in the numbers it’s -12 - (-3) over -4 - 8, when simplified you get 3/4. parallel lines have the same slope because they don’t intersect so the slope for a would be 3/4. the slope for b would be -4/3 because the slope of a line perpendicular to an existing line is the opposite reciprocal of the slope to the first line. if the given line’s slope is 3/4 then the reciprocal is 4/3 and the opposite of positive is negative so that’s why it’s -4/3. i know that my explanation can be kinda confusing but i hope i helped :)