You can use desmo its a site that helps graph
If you mean "how to write the sum", the answer is

The result of this sum is
, because you start from 2 on the number line and take 3 steps to the left (negative integers mean going left, positive integers mean going right)
In this question weight of a flea and an ant is given, but their units are different. So comparing and finding out the weight of flea and ant would be difficult. First thing that needs to be done is to bring the units of both the flea and the ant under same unit.
Weight of flea = 8 decigrams
Weight of ant = 3 milligrams.
Now let us convert the weight of the flea from decigrams to milligrams.
We already know that
1 decigram = 100 milligram
Then
8 decigrams = 100 * 8 milligrams
= 800 milligrams
Then
The weight by which the flea is greater than the ant = (800 - 3) milligrams
= 797 milligrams.
So the flea weighs 797 milligrams more than the ant.
If I'm correct you, add the two prices together, getting the price of $429.99