Rosemary and Darwin are discussing how to find the value of -28 + 45. Rosemary says the value of -28 + 45 = -73. Darwin
says the value of -28 + 45 = 17.
Who is correct, and why?

Darwin

Step-by-step explanation:

-28+45=17 because 45-28=17. To prove, do the math!

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.