Alex,
Sorry, but I disagree. In fact, I think the question is wrong. First of all, there is one vital piece of information missing, and that is what datum is set on the altimeter. Without that piece of knowledge, you can't answer the question.
If 1013 is set, then alex has started off on the correct lines - but when do you ever fly around at MSA with 1013 set? Even then, to get a true altitude you would need to take the temperature into account. But it's so rare to care about the temperature when you're on 1013 (because you're normally well above MSA, so temperature errors don't matter) that none of the textbooks will tell you how to do this.
If either QNH or QFE were set, you would still need to take the temperature into account. But here there is another piece of information missing, and that is the elevation of the airfield whose QFE or QNH you are using. You need this because that is your datum altitude - the temperature correction will be a percentage of your height above this datum.
So I don't believe it's possible to answer the question, on two counts.
FFF
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