You applied the rule improperly. When dividing exponents, you subtract the exponent of the denominator <em>from</em> the exponent of the numerator, not the other way around. The exponent you should have gotten was 
<span>t+3/2 = 1/2 // - 1/2
t+3/2-(1/2) = 0
t+3/2-1/2 = 0
t+1 = 0 // - 1
t = -1</span>
17/7 cannot be put into a whole number, but it can be put into decimal form. The estimated decimal number is 2.43. You just divide 17 by 7 and then round.