Answer:
D
Step-by-step explanation:
Nine and a half, I believe :)
Factor r 4 t 4 out of 5 r 8 t 5 − 3 r 4 t 4 . r 4 t 4 ( 5 r 4 t − 3 )
With 10 to the power to a negative number, it's easier.
Here's a trick: The negative number is the places to the right of the decimal. The last number is a 1, while the rest are 0s.
From this, we get: