Answer: v = 3/7
Step-by-step explanation:
5 ( 6 - 4v ) = v + 21
30 - 20v = v + 21
30 - 20v - v = 21
30 - 21v = 21
-21v = -30 + 21
-21v = -9
v = -9/-21
v = 3/7