It's extraneous. I know this because it leads to a straight answer.
3x+5+15=2x+5
26x+155x=2x+5
26x+15=10x2+25x
26x+15−(10x2+25x)=10x2+25x−(10x2+25x)
−10x2+x+15=0
x=−b±√b2−4ac2a
x=−(1)±√(1)2−4(−10)(15)2(−10)
x=−1±√601−20
x=120+−120√601 or x=120+120√601
x=120+−120√601
x=120+120√601
x=120+−120√601 or x=120+120√601
Hoped I helped!