Idon’t know what the formula is and how to work it out, .

Whenever you have straight lines on a graph they mean that that they only have either an x value or a y value. Normally you would have both, right?
so, 
1. what is k doing? Its a horizontal line so it will be all y values at the point where it crosses the y axis. Here it looks like it crosses at the 8 mark so the value of this is y=8
2, line 1 crosses the x axis so it is all x values. here it crosses at 1 so its equation is x=1 the line parallel to it crosses x at 7 so its equation is x=7
The last line to describe crosses y at 2 so its equation is y=2.
3. The area is easy just count all the squares inside the figure. Or the formula is length times width.

Xis equal to three