The best real-world problem that models the equation \(0.08x = 0.06x + 140\) is:
A certain sum yields $140 more in interest when the interest rate is 8% than when it is 6%.
This statement correctly reflects the mathematical equation, where \(x\) represents the principal sum of money, \(0.08x\) represents the interest earned at an 8% interest rate, and \(0.06x + 140\) denotes the interest earned at a 6% interest rate plus an additional $140.