Answer:
B: 7t(8s - 3)
Step-by-step explanation:
Method 1: check by expanding each of them
A: 7(8st - 3t)=56st-21t
B: 7t(8s - 3)=56st-2t
C: 3t ( 18s - 7)=54st-21t
D: 7s ( 8t - 3t)=56st-21st
Method 2: the common factors of 56st and 21t is: 7t
56st/7t=8s
-21t/7t=-3
56st-21t=7t(8s-3)
