If 2 log x = log 250 - 1, the value of x is :

1. 17

2. -5

3. 5

4. 10

If log₃ x - log₃ 2 - 1 = 0; the value of x is :

1. 3

2. -3

3. -6

4. 6

If x = 1 + log 2 - log 5, y = 2 log 3 and z = log a - log 5; find the value of a, if x + y = 2z.