Your answer is A. Y=5- 1/3x
T=5
4=2+2/5t
Subtract 2 from both sides.
2=2/5t
Multiply both sides by 5/2.
t=5
That's a 33% increase.
I calculated this using the formula:

Where n = the new value (16 in your question), o = the old value (12 in your question) and the result is outputted as a percent increase. You can check that this is correct by finding 33% of 12, adding the result to 12, and checking that the result equals your "new" number.
Note that 33% is only an approximation as your question requires a number rounded to the nearest whole.
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