Answer:
(-1,1,3)
Step-by-step explanation:
midpoint = (x1+x2/2, y1+y2/2, z1+z2/2)
midpoint = ( (-6+4)/2, (3+-1)/2, (4+2)/2 )
midpoint = (-2/2, 2/2, 6/2)
midpoint = (-1, 1, 3)
207$ - 15$ = 192$
192$ : 8 = 24$
Answer: Each book costed 24$.
The ratio is 30 : 9 = 10 : 3
