Simple.....
always remember the y-intercept is where your line hits the y-axis... or where it hits the vertical axis...
As we can see this line hits the y-axis at (0,3)-->> y-intercept=3
Thus, your answer.
Part A
Your problem statement already shows you the conversion.
Bottles purchased: 5×10¹⁰
Bottles recycled: 8.3×10⁹
Part B
The ratio of bottles purchased to bottles recycled is
... (5×10¹⁰)/(8.3×10⁹) = 0.6×10¹ = 6.0
The number of bottles purchased is 6 times the number of bottles recycle.
The answer is 20 since 1/5 of 20 is 4, and 20 + 4 = 24.