How do i solve this system of equations

If ac = 12 and ab=7 is it possible that bc =10

An equation representing lyle’s hedge-trimming business is a = 12n - 300 where a is the amount of profit or loss in dollars and n is the number of hedges trimmed. how would the graph of lyle’s business change if the equation a = 10n - 300 represented his business? the graph would be flatter. the graph would be steeper. the graph would start closer to the origin. the graph would start lower on the y-axis.

Which expression gives you the distance between the points (5,1)and(9,-6)