The cost to purchase a song from itunes is $0.99 per song. to
purchase a song from napster, you must be a member. the
napster membership fee is $10. in addition, each purchased
song costs $0.89. how many downloaded songs, d, must be
purchased for the monthly price of napster to be the same as
itunes?

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.

i use my brain for prombles like this maybe you could try it

step-by-step explanation:

what i would say the best answer is a. 40.5

a. 12.5 kg

step-by-step explanation:

f = ma

so

m = f/a = (2500 n)/(200 m/s²) = 12.5 kg

1 n = 1 kg·m/s²