Hi,
SP=Selling Price
CP of dress= $ 89.47
percent of mark up = 50%
SP without tax= 100+ mark up % /100 * CP
SP without tax= 100+50/100 * 89.47
SP without tax= 150/100 * 89.47
SP without tax= 1.5 * 89.47
SP without tax= $ 134.205
tot. SP(SP with tax)= 100 + tax %/100 * SP
SP=100 + 7.6/100 * 134.205
SP= 107.6/100 * 134.205
SP= 1.076 * 134.205
SP= $144.40458
Hope this helps you.