Question 1052612
The sum of the angles in any triangle is 180.
{{{A+B+C=180}}}
So you also know,
{{{A=20+2B}}}
and
{{{A=C-45}}}
So then,
{{{A-20=2B}}}
{{{B=(A-20)/2}}}
and
{{{C=A+45}}}
Substitute into the top equation,
{{{A+(A-20)/2+A+45=180}}}
Multiply both sides by {{{2}}},
{{{2A+A-20+2A+90=360}}}
{{{5A+70=360}}}
{{{5A=290}}}
{{{A=58}}}
So then,
{{{C=58+45}}}
{{{C=103}}}
and
{{{B=(58-20)/2}}}
{{{B=38/2}}}
{{{B=19}}}