He earned 505.80 a week without the increase. With the increase in wages he earns 604.8 with the increase
2n - 4 (the difference means you're subtracting, twice a number is 2n and then 4 is 4, so it equals 2n - 4)
I showed my work and answer in this picture. When simplifying square roots you can split them into a perfect squares root time the remainders