Question 343331
You need to solve 2 equations simultaneously.
First name the variables.
Let {{{A}}} be the angle.
Let {{{C}}} be the complement.
1.{{{A+C=90}}} By definition.
That's the first equation.
Then also,
2.{{{A=15+2C}}} 
Now you can substitute eq. 2 into eq. 1 and solve for {{{C}}}.
.
.
.
{{{A+C=90}}}
{{{(15+2C)+C=90}}}
{{{15+3C=90}}}
{{{3C=75}}}
{{{highlight(C=25)}}}degrees
Then from eq. 1,
{{{A+C=90}}}
{{{A+25=90}}}
{{{highlight(A=65)}}}degrees