Answer:
15
Step-by-step explanation:
Distance between two points is = √(x2 - x1)² + (y2 - y1)²
x1 = -5, y1 = 4; x2 = 7, y2 = -5
|PQ| = √(7 - (-5))² + (-5 - 4)²
|PQ| = √(7 + 5)² + (-9)²
|PQ| = √(12)² + 81
|PQ| = √144 + 81
|PQ| = √225
|PQ| = 15
if n(a)=4
if n(b)=3
then n(c)= 2
