MAT Livestream 2020

Just the maths from the MAT livestream on 30 July 2020.
We're running a maths problem-solving livestream with a particular focus on Mathematics Admissions Test problems, live at www.maths.ox.ac.uk/r/mat every Thursday.
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0:00 MAT 2015 Q5
17:45 MAT 2010 Q5
27:52 MAT 2013 Q1J
Errors in this video
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Download the questions in this video at www.maths.ox.ac.uk/system/fil...

[@pragalbhawasthi1618]

My answer to MAT 2015 Q5 is the following:
g(a,b)=s(b,m(g(a,p(b)), p(a))
This one works as well because the iteration continues for one step longer because of just b (than what's in the video), and finally we add an extra 1 (because of p(a) ), so the net result is still a+b

[@user-ei3xr8hb6z]

For 2015 Q5, I use the (-b) before the first coma, and a for the second coma, and m(g(a,m(-b))) after the second coma. Help me to check whether it works.