6.) The line should be in the form y = mx + b where m is the slope and b is the y-intercept.
You know the y-intercept, or b, is 0 because that's where it intersects the y-axis.
You know that the slope should be -2 because it goes 1 to the x and -2 to the y, and slope is y/x.
Ultimately, your equation should be y = -2x or answer choice a.
7.) The independent variable, or the x, should be miles because the calories is affected by the number of miles, not the other way around. This should be answer choice b.)
Hope this helped! ^-^