Answer: Jeremy charged $20 15 times
Step-by-step explanation:
Let x represent the number of times Jeremy charged $20.
Let y represent the number of times Jeremy charged $25.
The total number of lawns that he mowed is 35. It means that
x + y = 35
He charged either $20 or $25 a lawn. The total amount that he made from mowing the lawns is $800. It means that
20x + 25y = 800- - - - - - - - -1
Substituting x = 35 - y into equation 1, it becomes
20(35 - y) + 25y = 800
700 - 20y + 25y = 800
- 20y + 25y = 800 - 700
5y = 100
y = 100/5
y = 20
x = 35 - y = 35 - 20
x = 15