an equilateral triangle has 3 equal sides by definition.
so we know that x+2 = -2x+20 because we're told that those are both lengths of the triangle's sides. let's solve for x.
x+2 = -2x + 20 add 2x to both sides. 3x + 2 = 20 subtract 2 from both sides. 3x = 18 divide both sides by 3. x = 6
now, let's find the length of the sides. plug 6 into one side, which is x+2. 6+2 = 8. so each side's length must be equal to 8. let's just check to make sure we didn't make a mistake. if this is correct, then -2x + 20 should also = 8.
-2(6) + 20 -12 + 20 8.
so we know that the sides = 8. let's see if 14 - x or 2x+4 are equal to 8 when we plug in 6 for x.
14 - 6 = 8. so 14-x could be a length for a side.
2(6) + 4 = 12 + 4 = 16. so 2x + 4 can not be a length for a side.
