if you mean that 1 interior angle of an equilateral triangle is 5x+16
then
all interior angles in an equilateral triangle are equal
all interior angles in a triangle add to 180 egrees
so if 1 interior angle is 5x+16, then 3(5x+16)=180
solve or x
divide both sides by 3
5x+16=60
mins 16
5x=44
x=8.8 degrees
