Question 986621
1.{{{A1=A2}}}
2.{{{A1+A3=90}}}
3.{{{A2+A4=90}}}
From 1,2, and 3,
{{{A3=A4}}}
Substituting,
{{{A1=A2=47}}}
.
.
.
{{{47+A3=90}}}
{{{A3=43}}}
So then,
{{{A4=43}}}