Both Todd and Zack earn the same salary. Todd spent $716 and Zack spent $128. Then Zack had 4 times the amount of money Todd had left. How much is their salary?

Please tell me how and what your answer is?

Let x = salary

x - 128 = 4(x - 716)

x - 128 = 4x - 2,864

I'll let you solve for x.