A possible mistake in the solution of exercises sheet 2

in the excercise sheet 2, question 3.b, in the solution i found this
i’m not sure if this is a mistake or am i the one who is mistaken here
i can see that we came to this answer by extending the right hand term by a zero at the beginning so it becomes 010000 and then apply 100110 + 010000, but shouldn’t we have extended it propagating the most significant digit since we are in signed notation? and apply 100110 + 110000 and have 1010110 =-42 as an answer ?


there is no special extension requiered for the right number. You only evaluate the number as a signed number after you have added the two numbers together.