Which method should be used to solve for x?

1. Estimated Distance = 15.5 miles

Actual Distance = 14.5 miles

2. Price of the wallet = $31.95

Sales tax = 7.5%

Total Cost = Price of the wallet + Sales tax

Total Cost = 31.95 + 0.075 × 31.95

So, Total cost of the wallet = $34.35

3. Total Monthly sales = $4125

Commission made = $165

4. Principal = $12000

Time = 3 years

Rate of interest = 15%

                          = 0.15

Simple Interest = Principal × Rate × Time

Simple Interest = 12000 × 0.15 × 3

Simple Interest = $5400