What does it mean to be proportional?
For two numbers to be proportional, they need to be directly increasing or decreasing in a constant ratio.
If Donny makes $9.75 per lawn, we can make a table that looks like this:
1 Lawn = $9.95
2 Lawns = $19.90
3 Lawns = $29.85...
And so on.
You can see this is proportional because it has a constant ratio between both elements.
(1 to 9.95)
So, it is proportional.