18. (if you needed it)
The triangle is an equilateral triangle, it has 3 congruent/equal side lengths and 3 congruent angles.
To find "z", you can set the sides equal to each other (you can just do two sides since they are all suppose to be the same lengths)
z + 5 = 4z - 4 Subtract z on both sides
5 = 3z - 4 Add 4 on both sides
9 = 3z Divide 3 on both sides
3 = z
Plug this into one of the sides
z + 5
3 + 5 = 8 Each side is 8
[proof]
z + 5
3 + 5 = 8
4z - 4
4(3) - 4
12 - 4 = 8
3z - 1
3(3) - 1
9 - 1 = 8
19. This is an isosceles triangle, which is a triangle that has 2 congruent sides and 2 congruent angles. (The red tick marks shows that the sides are the same/equal)
Since the 2 sides are the same length, you can set them equal to each other to find "x":
2x + 6.8 = 8x + 1.4 Subtract 2x on both sides
6.8 = 6x + 1.4 Subtract 1.4 on both sides
5.4 = 6x Divide 6 on both sides
0.9 = x
Now that you know x, you can find the sides:
2x + 6.8
2(0.9) + 6.8
1.8 + 6.8 = 8.6
8x + 1.4
8(0.9) + 1.4
7.2 + 1.4 = 8.6
The two side lengths are 8.6
