2 sides of an equilateral triangle measure (y+10) units and (y^2-2) units. If the perimeter of the triangle is 21 units, what is the value of y?

Question

I was trying (y+(y+10) + (y^2-2)=21
got to y^2+2y+-13 and wasn't sure how to proceed.
Or should I take a side (y^2-2)*3=21?
I ended up with 3 but the other side ends up with -3. Could this be a typo?

Answer 1

It appears that the 3rd side is y, so yes, that means

y + (y+10) + (y^2-2) = 21
y^2+2y+8 = 21
y^2+2y-13 = 0

now use the quadratic formula. If you want an integer or rational answer, there must be a typo somewhere.

Answer 2

You know the perimeter is 21 and, it's equilateral. Which means all sides are equal so therefor 21 divided by 3 = 7.