Geo help on this question very hard

Find the magnitude, correct to two decimal places, made by each of the following with positive direction of the x axis a) y= x the answer is 45° but i don’t know how

Xy x xy if a and b are positive integers such that a*b=9 and b*a=72 what is the value of a/b

If a revenue in total for a month was $9,950, fixed expenses were $9,000, and variable expenses were $300 what would be the total profit/ loss for the month?