We can write this as an equation:
[tex]800 + 20x = 600 + 30x[/tex]
where x is the number of weeks.
To solve, we subtract 20x from both sides and subtract 600 from both sides:
[tex]800 - 600 = 30x - 20x \\ 200 = 10x[/tex]
Then, we simplify by dividing both sides by 10:
[tex] \frac{200}{10} = \frac{10}{10} x \\ 20 = x[/tex]
Thomas and Ken have to work 20 weeks for their earnings to be the same.