I need help with 2 exercises.

Quarter of whole work was done with a machine, which' power is 4kW,
then a new machine was taken into use.
The whole work was done with 6kW power.
1. What was the power of new machine?
2. How much time was saved percentually by doing 3/4 of the work with new
machine, compared to if the whole work was done with the 1st machine.
4*1/4 + x*3/4 = 6

1 + 3x/4 = 6


4 + 3x = 24


3x = 20




x = 6,66


Have I done it correct? And a little help with the 2nd one too, please.

Heating an amount of water from 0(not ice) to 100°C took 15 minutes. How much time did it take to turn the water into steam?
L/c = 550

Regarding your last question. Unless I'm missing something Oc is ice and 100c is boiling. Am I missing something?

Regarding your last question. Unless I'm missing something Oc is ice and 100c is boiling. Am I missing something?
Water can be 0C without turning into ice.
Still help needed!