You have to subtract both sides by 64 and you will get,
-50 = 5z. Then divide both sides by 5, and you get -10 = z.
3 to the 4th power = 3x3x3x3 which is 81 :)

in exponent form and in word form it is 10 to the 5th power
I think Ollie payed $1,500 back.