Physics question momentum

Question seems to be asking for speed?

It's bouncing back in the opposite direction... subtracting a negative number is the same as adding a positive number.

Hi, please could i have help on this question? I don’t understand where i went wrong? The question is asking to calculate the speed after the collision. Change in momentum= mass times change in velocity. The change in velocity will be final-initial velocity so surely the markscheme for 2 ci should read v-2.8 instead of v+2.8 (2.8 was the initial velocity?
Here is the question: https://app.gemoo.com/share/image-annotation/632443787613372416?codeId=DWlKz2oB9XWZr&origin=imageurlgenerator
https://app.gemoo.com/share/image-annotation/632444133144338432?codeId=vJ3dJ4xog5mrO&origin=imageurlgenerator
Here is the markscheme: https://app.gemoo.com/share/image-annotation/632444400736735232?codeId=DWlKzlKG9R2wr&origin=imageurlgenerator

Thanks!!

But if it is bouncing back in the opposite direction, wouldn’t the final velocity be negative so it should be (-v2-+2.8) so (-v2-2.8) which still does not give the same answer?

If we use the definition
change in momentum = final momentum - initial momentum
we can notice a few things:
• the direction of final momentum is pointing to the left after collision
• the direction of initial momentum is pointing to the right before the collision
• let use "arrows" to do the subtraction of the momenta, change in momentum will be
$\leftarrow - \rightarrow = \leftarrow + (-\rightarrow) =\leftarrow + (\leftarrow) = \leftarrow$
• the change in momentum is pointing to the left and the change in momentum is given as positive in the question, so we can assume that the positive direction is pointing to left
As a result, we can write
change in momentum = mass × (final vel − initial vel) = m(v − (−2.8)) = m(v + 2.8)
The last part (v + 2.8) “can” be viewed as the addition of final speed and initial speed to compute the change in momentum.