Given 
 Grant and Pedro are comparing their stocks for the week
On Monday, their results were opposite.
 for Monday if Grant lost $4
 Explain how you would graph their results for Monday.
To proof
let us assume that value of stocks after a week = x
As given in question
 for Monday if Grant lost $4
i.e x= - $4
result were opposite for grant and pedro.
thus
 for Monday if Pedro gain $4
i.e x = $4
Therefore two values are
x = -4  and x = 4 is shown in graph given below.
This shows that x = -4 lies left of 0 to x-axis and x = 4 lies right of  0 to x- axis.