Question 171120
lets call the tens digit a and the ones digit b
:
a+b= 13...eq 1

2a=b-1....eq 2
:
lets re write eq 1 to a=13-b and take that value and plug it into eq 2
:
2(13-b)=b-1
:
26-2b=b-1
:
3b=27
:
{{{highlight(b=9)}}}
:
{{{highlight(a=13-9=4)}}}
:
number is {{{highlight(49)}}}

: