need help on grammer

[myc]

Everyone who comes to visit sees that 80 percent of the chips (have, has) been eaten by Dick and Bob.
The answer is has, but shouldn't it be have been eaten, since the chips are eaten by two people, not just by one person?

also Is this sentence correct?
In addition to the raise and a company car, Bob demanded a four-day work week.


Is the sentence parallel? Should the raise be changed to a raise?
Thanks

[Mister Micawber]

.
1-- Percents can be singular or plural, and it has nothing to do with the number of eaters; it depends on the notional countability of the noun:

80% of my friends are gay.
80% of the orange juice has been drunk.

B-- It depends on the context: if the raise has been mentioned previously but the car has not, then the current articles are appropriate.
.

[myc]

have- singular
has- plural

is this right?

[Mister Micawber]

.
No. Have is all persons except 3rd person singular:

I have
you have
she has

we have
you have
they have
.