Y=3x has a positive slope, and Y=-3x has a negative slope.
7%, 13%, 0.15, 4/25, 21/100, 0.28
Ignore the decimal places and do 789x38 and you get 29982. Now all you have to do is put the decimal places back. Since 789 was 7.89 it had 2 decimal places and 38 had 1 you have to move 29982 three decimal places to the left making your final answer 29.982.