So the watch costs 75.99 including sales tax.
The sales tax is 6.25% of the value of the watch.
100% of the value of the watch is n.
100% + 6.25% of the value of the watch is 106.25/100 * n = 75.99
Let's calculate the sales tax...
[tex]\frac { 106.25 }{ 100 } \cdot n=75.99\\ \\ 106.25\cdot n=7,599\\ \\ n=\frac { 7,599 }{ 106.25 }[/tex]
[tex]\\ \\ =71.52\\ \\ Sales\quad Tax\quad is\quad Therefore:\\ \\ 75.99\quad -\quad 71.52\quad =\quad 4.47[/tex]