Question

S/A=4.5,D/A=4.5, N/E =.80
& A = D + E solve for N/S

Answer 1

S=4.5A and D=4.5D, so S=D

N=.8E
A=D+E

So A=S+E=S+N/.8

dividing by S
A/S=1+N/S (1/.8)

but A/S=1/4.5 so solve for n/s

Answer 2

im still confused.

Answer 3

Bob meant to write:
S=4.5A and D=4.5A, so S=D

What other steps are confusing you?

You end up with
A/S = 1 + (N/S)(1/.8)
but you already knnow that

A/S = 1/4.5 , so
so solve for N/S.

(N/S)*(5/4) = (A/S) -1
= (2/9)- 1 = -7/9
N/S = (4/5)(-7/9) = -28/45

Check my math