Answer:
Just substitute 0 instead of f (x),therefore

The answer option is C
Okay so i cant just post what the answer is i have to type something.
but anyways this is the answer: t= 4.56
Step-by-step explanation:
6. 7x + 7y = -11
7. -1x + 8y = 12
8. 9x + 11y = -7