We know that 2x+7 = 27, so that means that if 2x+7 = 3x+1 then 3x+1 = 27 also but we are told that 3x+1 = 28, so that means that 2x+7 does not equal 3x+1
Standard deviation measures how spread out the data is. If you add 8 to all the data values, the distribution of data moves to the right (on a graph) 8 units. The shifted data are no more and no less spread out than before. The standard deviation does not change.
