So...the diameter is increasing at a rate if 2cm/minute, therefore the radius (1/2 the diameter) is increasing at half the rate. You will learn how to calculate the rate of change at a specific point in time in calculus.
In the question it is given that,
The students at Midtown Middle school sold flowers as a fundraiser in September and October. In October, they charged $1.50 for each flower
And the October price was a 20% increase of the September price.
Let the price of the flower in October be $x
So we have

So the price of the flower in Septembet is $1.25 .
25 + 100i is correct because -5 squared is 25 and the the square root of -100 is 100i or 10i in its simplest form.