Number 5 should be no solution becuase the n's cancel out.
For 6: Part A is -2 because slope represents the change in weigh/change in time (-2/1 or -2) Part B is y=-2x+231 (-2 is the slope and 231 is the y-intercept) For part C, based on the slope, we can find that her weight will go below 200 at week 16 when it is 199
