how do I solve for x to get x=9729 miles/year

Example A minivan is quite functional, but it only averages 20 miles per gallon (mpg). somewhat newer vehicle (roughly the same functionality) that averages 26 mpg S/he can sell her/his current minivan for $2800 and purchase the newer vehicle for $4000. Assume a cost of gasoline at $4.00 per gallon. How many miles per year must the owner drive if she wants to recover her his investment in three years? Assume an interest rate of 6% , zero salvage value for either vehicle after three years, and identical maintenance cost The owner has found a 4 - 5 6 57 THE UNIVERSITY OF TENNESSEE CHATTANOOGA Bridges Beyond the Classroom 58 59 44 Solution Current minivan G($4.00) (P/A, 6%, 3) PW1 $2, 800+ New vehicle ($4.00)(P/A,6%, 3) PW2 $4,000 + 26 Equating these, and solving for x, we find 9, 729 miles/year THE UNIVERSITY OF TENNESSEE CHATTANOOGA Bridges Beyond the Classroom 44