Rewrite in slope intercept from y=mx+b y=1-3x+11/3

Divide both the numerator and denominator by 9 to get;

Convert the improper fraction to a mixed number;
U do 4/20 = p/100 then u cross multiply the 4 with 100 getting u 400, then divide the 400 by 20, giving u the answer of 20%