Logarithms help

Question

Write the expression as the sum or difference of logarithms.

(1)        log[b][a(b-19)]

(2)        log[3](81/y)

Use the power property to rewrite the expression.

(1)        log[7]r^(3)

(2)      log[6]√5:(y)

(3)     log[18]a^(-1)

(4)       log[3]√4:(y)

write the expression as a single logarithm with coefficient 1. Assume that all variables represent positive real numbers.

(1)    5log[b]x-7log[b]y^(6)=log[b]

Answer 1

(1)  log _b [a(b - 19)] = log _b a  +  log _b (b - 19)

(2)  log ₃ (81/y) = log ₃ 3⁴ - log ₃ y = 4 - log ₃ y 

(1) .... = 3 log ₇ r
(2) .... = What does the colon between 5 and "y" stand for?