If (3x - 9) : (5x + 4) is the triplicate ratio of 3 : 4, find the value of x.

If x, 2, 10 and y are in proportion, the values of x and y are respectively :

1. 0.2 and 0.25

2. 0.2 and 50

3. 0.4 and 50

4. 0.4 and 25

If x : y = y : z, then x² : y² is :

1. 1 : x

2. x : y

3. x : z

4. z : x