let us take any two points here (5,20) and (7,30)
now let us use slope formula to get its slope
slope =5
now let us use one coordinate (say (5,20)) and slope to get the y intercept
20= 5*5 +b
b=-5
plugging the values of b and m in the given equation we get
y=5x-5
or c=5m-5