Question 946932
Because in a parallelogram, opposite angles are equal and you know the sum of all of the angles is equal to 360.
{{{X+Y+X+Y=360}}}
{{{X+Y=180}}}
Now if {{{X=Y}}} then,
{{{X+X=180}}}
{{{2X=180}}}
{{{X=90}}}
So then,
{{{Y=90}}}