2x + 3y = 25 ( y=kx+m )
3y = -2x + 25 ( 留Y,其他都往右侧移动 )
y = ( -2 / 3 ) x + 25 / 3 ( 化简,已经最简就不用化了 )
k = (-2) / 3 m = 25 / 3