We can generalise this by finding the equation of the line.
The gradient is: 15
We can take when x = 10, and y = 150 to find the equation of the line.
y - 150 = 15(x - 10)
y - 150 = 15x - 150
y = 15x
Thus, when x = 80, y = $1200 (ie B)
0.981 is less then 1
2.3 is greater then 1
0.981 < 2.3 (it is less then)
Note what i actually represents.
i is the very basis of a whole new level of counting. When finding discriminants, we often say that a quadratic has no
real roots if the discriminant is 0. Needless to say, there are roots, they are just imaginary.

, in real terms, is non-existent. That is, there are no numbers in the real number system that when multiplied by itself produces a result of -1. This is what i unit represents.
Let's tackle this problem in smaller steps.
Let's first expand our brackets.
(i - 7i)² = (-6i)² = 36i²
Now, let's distribute the xi.
xi(i - 7i)² = xi(36i²) = 36xi³ =

= -36xi