Hey there!
This situation can be represented by the following equation:
y = 20 + 20x
This is because she starts without any time passing with 20 pounds of cans and collects 20 more pounds every week.
So when x = 0, y = 20.
The variable y is the number of pounds of cans collected, while x is the number of weeks passed.
If we want to find the number of pounds of cans she has after 10 weeks, we have to substitute x = 10 like this:
y = 20 + 20(10)
Multiply 20 x 10.
y = 20 + 200
Add 20 + 200.
y = 220
Your answer is 220 pounds, the second option shown!
Hope this helps!