Question 1151396
<pre>
Let A = first angle
Let B = second angle
let C = third angle
</pre>the second angle in a triangle is one-third as large as the first.<pre> 
{{{B = expr(1/3)A}}}
</pre>the third angle is two-thirds as large as the first angle.<pre> 
{{{C = expr(2/3)A}}}
</pre>find the measures<pre>
They are the three angles of a triangle, so their sum is 180°.

{{{A + B + C = 180^o}}}

Substitute for B and C

{{{A + expr(1/3)A + expr(2/3)A = 180^o}}}

Multiply through ever term by 3

{{{3A + A + 2A = 540^o}}}

{{{6A=540^o}}}

{{{A=90^o}}}

{{{B = expr(1/3)A}}}
{{{B = expr(1/3)90^o}}}
{{{B = 30^o}}}

{{{C = expr(2/3)A}}}
{{{C = expr(2/3)90^o}}}
{{{C = 60^o}}}

It's a 30°-60°-90° right triangle

Edwin</pre>