Okay so this is a simple multiplication problem (for the most part).
If a runner is running at 2.4 m/s what is the distance it will travel in lets say 2 minutes. <----Second time interval
Well first you'd want to convert those minutes into seconds. So there are 120 seconds in 2 minutes.
Now into the multiplication, if for every second the runner is running 2.4 meters then you would multpily 2.4 by however many seconds
(2.4) x 120 = 288 meters
To add on to Cavallin ^^^
Theres also this thing called the double negative rule where if you have
(-2) - (-7) If you take away the parenthesis you see two negative symbols right next to each other
If ever you see that -2 - -7 the double negative turns into a positive so your new problem would be
-2 +7 = 5