We have here a case of a linear situation. We have that:
1. We have a fixed cost of $4.99.
2. And we need to add $0.30 for every ounce the package weighs.
The equation that represents the total cost of the shipping is:
We can see that per every ounce, we need to multiply it by $0.30 to obtain the total cost (plus the fixed cost of $4.99).
We expressed the equation in the slope-intercept form (y = mx +b).