Please help! I'm stuck on this one :(

Given that (x-3) is a factor of f(x)=x^3+ax^2-x-6, find a and hence the number of real roots or the equation f(x)=0

Write an equation of a line in slope intercept form that is perpendicular to the line 2x -3y = 12 and passes through the point (2, 6).

Tabby sells clothing at a retail store, and she earns a commission of 6.25% on all items she sells. last week she sold a pair of jeans for $32.50, a skirt for $18.95, and 2 blouses for $14.95 each. what was tabby's total commission? a $4.15 b $5.08 c $81.35 d $348.60