Answer:
The equation which is used to find number of hours is

Rico worked 15 hours after school job last week.
Explanation:
Given:
Money earned after school job = $8 per hour
Money Earned in Moving neighbors lawn = $20
Total Money earned = $140
We need to find number of hours Nico worked.
Let number of hours Nico worked be x.
Now Total Money earned is equal to Money Earned in Moving neighbors lawn plus Money earned after school job multiplied by number of hours he worked.
Hence framing the above sentence in equation form we get;

Hence the equation which is used to find number of hours is

Solving the above equation we get;

Hence Rico worked 15 hours after school job last week.