Sorry I'm quite bad at maths, but wanted to find out
a) 4^(x - 1) + 0.5 = (3/4).2^x
b) 4/(x - 6) > 5
b) First things first:
Since the right hand side is positive then it follows that the left hand side must also be positive, this sets a lower bound of and we do not need to worry about the direction of the inequality changing
This gives and you can solve for x in the normal way.