Question 1125493
In triangle {{{ABC}}}, the three angles

->{{{A+B+C=180}}}....eq.1

if {{{B}}} is {{{15}}} less than {{{two}}} times {{{A}}},we have

{{{2A=B+15}}}

{{{A=(B+15)/2}}}....eq.2


if {{{C}}} is {{{3}}} degrees {{{larger}}} than{{{ B}}},we have
{{{C=B+3}}}....eq.3


go to {{{A+B+C=180}}}....eq.1, substitute {{{A}}} and {{{C}}} from eq.2 and eq.3

{{{(B+15)/2+B+B+3=180}}}..........solve or {{{B}}}

{{{2(B+15)/2+2B+2B+2*3=180*2}}}

{{{B+15+2B+2B+6=360}}}

{{{5B+21=360}}}

{{{5B=360-21}}}

{{{5B=339}}}

{{{B=339/5}}}

{{{highlight(B=67.8)}}}


then 

{{{A=(67.8+15)/2}}}
{{{highlight(A=41.4)}}}


and

{{{C=67.8+3}}}
{{{highlight(C=70.8)}}}



check the sum:
{{{A+B+C=180}}}
{{{41.4+67.8+70.8=180}}}
{{{180=180}}}