You have to searh the x values that make f(x) = 0
Factoring this equation is very difficult.
You can divide by x+3 and you will find that the equation can be factored as
(x+3)(x-4)^2
That means that x = -3 and x = 4 make f(x) = 0
Then the points are (-3,0) and (4,0).
It looks like you had some of the numbers correct, but you just labeled it and rounded it incorrectly, and the teacher gave you super partial credit for it.
For my work, I'm assuming that side A is opposite of angle A and side B is opposite of angle B, etc...
combine like terms on the left side. you always go from left to right.