We can post the question using the following equation:
[tex]8x\text{ - 7 = 49}[/tex]Nelly makes $8 an hour, but she needs to pay her mother back $7. This is the first part of the equation. She needs to have $49 at the end. So, to solve the equation, we have:
[tex]8x\text{ = 49 + 7 = 56}[/tex]We add 7 to both sides of the equation. Now, dividing both sides by 8, we finally have the result of x.
[tex]\frac{8x}{8}=\text{ }\frac{56}{8}=\text{ x = 7}[/tex]Therefore, she needs to work for 7 hours to pay her mother $7 and has $49 in her account. (In your options Ob = 7).