Answer:
y = 36
Step-by-step explanation:
log4 (y – 9) + log4 3 = log4 81.
We know from the property of logs that if the bases are the same, when we subtract logs, we can divide what is inside
loga (b) + loga (b) = loga (b*c)
Lets simplify the expression log4( (y-9)*3) = log4 (81)
Since the bases are the same, what is inside the parentheses on the left hand side must be equal to what is inside the parentheses o the right hand side
(y-9)*3 = 81
Divide each side by 3
(y-9)*3 /3= 81/3
y-9 = 27
Add 9 to each side
y-9+9 = 27+9
y = 36