Find a gradient of a line that is parallel and perpendicular to this line with this gradient of 3 1/3

a parallel line has the same gradient, so the gradient would be 3 1/3

a perpendicular line has the negative inverse gradient of the original (eg. if the original gradient is 4/3 then the perpendicular gradient would be - 3/4 (all you have to do is change the + / - sign and flip the fraction), so in your case the gradient of the perpendicular line would be - 3/10 (since 3 1/3 = 10/3)