You add/subtract complex numbers simply by adding/subtracting real parts and imaginary parts.
So, the real part of this sum is the sum of the real parts:

And the imaginary part of this sum is the sum of the imaginary parts:

So, you have

Answer:
V = 2968.8 cm³ or 2969 cm³
Step-by-step explanation:
Given the radius, r = 7.5 cm, of a cylindrical coffee can whose height, h = 16.8 cm:
We can find the volume of a cylinder by using the following formula:
V = πr²h
Substitute the given values into the formula:
r = 7.5 cm
h = 16.8 cm
V = πr²h
V = π(7.5)²(16.8)
V = π × 56.25 × 16.8
V = 2968.8 cm³ or 2969 cm³
Therefore, the volume of a coffee can is 2969 cm³.
For the first one it would be 3(9 x 20)
And for the second one it would be 8