You must evaluate each of these options one by one:
A. A $55 jersey with 5% (.05) tax would equal 55 x (1+.05). This equation basically adds on 5% to the original $55. This equals $57.75
B. You can calculate this similarly to above, because it is asking you to add 10% on to the original $57. This would be 57 x (1+.10) = $62.70
C. This is clearly not an option because the original price of the jersey is already more than what Dave has.
D. This is asking you to deduct 25% of the original cost off of $85. You find this similarly to above, but this time you deduct 25% from the 1 --> 85 x (1 - 0.25) = $63.75
So you can see that Dave can only afford option A. Does that make sense?
