Solve.

a. log₅ (x + 8) + log₅ (x + 2) = log₅ 20x

b. log₃ x + log₃ (x – 2) = log₃ 15

c. 2 log₄ x – log₄ (x + 3) = 1

d. lg x + lg(x + 1) = lg 20

e. log₃ x + log₃(2x – 5) = 1

f. 3 + 2 log₂ x = log₂ (14x – 3)

g. lg(x + 5) + lg 2x = 2

h. lg x + lg(x – 15) = 2