Official Solution:A shop offers candy bars for sale either individually or in packs of 10. If buying a pack of 10 candy bars costs less than buying 10 individual candy bars, how much does the shop charge for a pack of 10 candy bars? Let's assume the cost of a pack of 10 candy bars is \(x\) and the cost of an individual candy bar is \(y\).
(1) Buying a pack of 10 candy bars costs $2 more than buying 8 individual candy bars.
From this, we have: \(x = 8y + 2\). With two unknowns and one equation, this is not sufficient to determine \(x\).
(2) Buying a pack of 10 candy bars costs 10 percent less than buying 10 individual candy bars.
From this, we have: \(x = 0.9 *10y\). Again, with two unknowns and one equation, we cannot determine \(x\).
(1)+(2) We have two distinct linear equations with two unknowns. Thus, we can solve for both \(x\) and \(y\). Sufficient.
Answer: C