It is called the median :)
This is going to be a linear function. On the horizontal axis, you will have weeks. On the vertical axis will be weeks. The slope of the line is 6/1 = 6, since she plays 6 hrs/week. At week 0 (the y-axis), the value will be 8, since that is the initial number of hours played. Therefore, the equation is: f(x) = 6x+8 f(x) is # hours x = #'d weeks.
It would take 2 hours. To complete the whole lawn you would need:

To make a whole, so to get that we multiply:

So we use the same number required for the whole lawn, and multiply it times the hours
The information provided is that you have smaller cubes that measure 1 cm on either of the three sides. In order words if you lie each cube side by side you would have the length/width/height of the indicate sides.
For a cube made up of 27 smaller cubes, you can determine the length of each side by factoring the entire size provided. That means for a cube made up of 27 smaller cubes you would have;

This means you would have 3 smaller cubes on the length, 3 smaller cubes on the width and 3 smaller cubes on the height.
Therefore, if you now have 150 of the smaller cubes, by factoring this you would have the following possibility;

This means you would have one side (length) 6 cubes, on another side (width) 5 cubes and on the third side (height) 5 cubes.
That means with 150 smaller cubes you could make a cube with the dimensions,

ANSWER:
The largest big cube you could make would be a 6 cm by 5 cm by 5cm big cube