For these problems use matrix (best way to do these problems in my opinion)

Lets see if i can set up so it shows up well on post:
We know that 70% passed written test and 80% passed flight
(bold will be given information)

---------------Passed Written Test----------Failed Written test----total
Passed Flight-------x-------------------------------y-----------------80%

Failed Flight---------z------------------------------w-----------------20%

Total----------------70%--------------------------30%--------------100%

A) w = 10%
So as you can see, if w = 10% y = 20% (y+w = 30%)
Then since x + y = 80%, x = 60%

B) y = 20%, so same as in A, x + y = 80%, so x = 60%

OA D.

oops forgot to bold given info, but I still think its pretty clear.

x=a+b-both+neither

i.e. 100=70+80-both+10.....

with both stmts we can find out both.... hence d