Robin ate some peanuts on Sunday. On Monday she ate 2 more peanuts than on Sunday. On Tuesday, Wednesday, Thursday, Friday, and Saturday she ate 2 more peanuts than the day before. By Saturday night she had eaten 77 peanuts in the whole week. How many peanuts did Robin eat on Wednesday?

Sunday peanuts = x
Monday peanuts = (x+2)
Tuesday peanuts = (x+4)

Then how would you write an equation?