Given that 1 gallon = 12.8 ounces
Target question: Did the tank contain more than 30 gallons of water when it started to leak?
Statement 1: The water leaked from the tank at a constant rate of 6.4 ounces per minute.
Rate => 6.4 ounces in 1 minute
x ounces in 60 minutes
x = 60 * 6.4 = 3.84 ounces per hour
1 gallon = 128 ounces
gallons = 384 ounces
$$y\ gallons=\frac{384\cdot1}{128}=3\ gallons$$
Therefore, water was leaking at the rate of 3 gallons per hour but then, the total capacity of the tank is unknown. Thus, the target question cannot be answered. Hence, statement 1 is INSUFFICIENT.
Statement 2: The tank became empty less than 12 hours after it started to leak.
This only tells us about the time it took for the tank to become empty. So, there is no information on the rate and capacity of the tank. Statement 2 is NOT SUFFICIENT.
Combining both statements together;
From statement 1 => rate = 3 gallons per hour
From statement 2 => rate = Time < 12 hours
If time = 5 hours, then the originally contained 5*3 = 15 gallons of water which is less than 30 gallons but if time = 11 hours, then the tank contained 11*3=33 gallons which greater than 30 gallons.
However, since a definite answer cannot be evaluated, then the target question cannot be answered. Both statements combined together are NOT SUFFICIENT.
