Place that is cooler than the other would have lower temprature

Representing temperature fall by negative and rise by a positive integer add both to the initial temperature

The greatest integer is -1 which is less than 0.

The difference between 15 and -4 and show the integer in rising or upward direction.

Represent withdrawing amount as a negative integer then add current balance and withdrawing amount

All Positive numbers are greater than 0.

Represent profit by positive integer ,choose appropriate sign for loss and add both

Above the surface must have opposite sign as that of below

The place that is cooler than the other would have a lower temperature

Fall is the opposite sign of rising in any quantity