Question 358801
By definition,
{{{Y+C=90}}}
.
.
{{{Y=6+3C}}}
Substitute,
{{{6+3C+C=90}}}
{{{4C+6=90}}}
{{{4C=84}}}
{{{C=21}}}degrees
Then,
{{{Y=6+3(21)}}}
{{{Y=6+63}}}
{{{highlight(Y=69)}}}degrees