the guy is trying to understand the problem not the answer, so show your working dak.
according to kershner's 'advanced pilots flight manual' the stall speed increases as the square root of the load factor increases.
1/cos 30 = 1.1547 load factor
square root of 1.1547 = 1.07456
7.456% increase
(pilots don't bother with decimals so 7%)