1. For every extra copy, Ivanna sells she gets an additional 120 dollars (+$120) and for every less copy she loses $120 dollars (-$120).
2. Ivanna's total pay is $2,400 if she doesn't sell any copies of History is Fun.
Step-by-step explanation:
Step 1:
y = 2,400 + 120x, where y is Ivanna's total pay and x is the number of copies of history is fun she sells.
To calculate the change is Ivanna's pay we find the difference in pay for two consecutive values of y.
We must calculate y when x is of consecutive values i.e. 1, 2, 3, 4 ...
Step 2:
We calculate the value of y when x = 1, 2 and 3.
When x = 1, y = 2,400 + 120 (1) = 2,400 + 120 = $2,520.
When x = 2, y = 2,400 + 120 (2) = 2,400 + 240 = $2,640.
When x = 3, y = 2,400 + 120 (3) = 2,400 + 360 = $2,760.
Step 3:
To calculate the increase in her pay for a copy, we subtract y when x = 2 from y when x = 3.
(y when x = 3) - (y when x = 2) = $2,760 - $2,640 = $120.
So for every extra copy, Ivanna gets an extra $120.
To calculate the decrease in her pay for a copy, we subtract y when x = 3 from y when x = 2.
(y when x = 2) - (y when x = 3) = $2,640 - $2,760 = -$120.
So for every less copy, Ivanna loses $120.
Step 4:
To calculate her pay when she doesn't sell any copies of history is fun, we substitute the value of x as 0 in y.
When x = 0, y = 2,400 + 120 (0) = $2,400.
So Ivanna earns $2,400 if she doesn't sell any copies of history is fun.
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