Question 24839
Let the two digit number be "ab".
a+b= 13 and a=b+5
=Using substitution rewrite the 1st equation as follows:
b+5+b=13
 2b+5=13
 2b = 8
  b = 4  (the unit's digit)
  a = b+5 = 4+5=9 (the ten's digit)
You have it right.

Cheers,
stan H.