This would be on a non-calculator paper and so it wants an answer in the form 2^n as without a calculator it is too difficult to work out. You can only do this multiplication if you change the 8 into 2^3 as then both multipliers are in the form 2^n. Then you use the rule that when multiplying 2^11 and 2^3 you add the powers to give the answer 2^14.