Answer:
1.8 × 10^10
Step-by-step explanation:
(7.2 × 10 = 72)
(72) ÷ (4 × 10^-9) = 1.8 × 10^10
Infinitely many because if you take the top equation and multiply it by 2 you get the same equation. That means that any number you plug in for x is a solution
