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 
Answer:
Height is 8cm
Step-by-step explanation:
A= bxh
9.6 = 1.2 x h
÷1.2
8 = h
Check:
8 x 1.2= 9.6cm
Hope this helps!