John paid 5% sales tax on his television, which cost $769 before taxes. what did the television cost in total?

For this case we can make the following rule of three:
 $ 769 > 100%
 x > 105%
 From here, we clear the value of x.
 We have then:
 x = (105/100) * (769)
 x = 807.45 $
 
 the television did cost 807.45 $ in total