The figure shown is an equilateral triangle. calculate the length of each side and give your answer in cm.
first side: 2x-7
second side: x+y-9
third side: y+5

Given at you have an equilateral triangle, all sides have the same length.

Therefore,
First side 2x-7 = Second side x+y-9 = Third side y+5

Let us look at the second and third sides for now:
x+y-9 = y+5
x = y+5 - (y-9)
x = y-y+5+9
x = 14

Then we look at equating the first and third sides:
2x-7 = y+5
y = 2x-7-5

Substitute x =14 in the equation above:
y = 2(14)-7-5
= 28-7-5
= 21-5
= 16

The length of the third side is:
y+5 = 16 +5 = 21

Given that the length of each sides are the same in an equilateral triangle, all sides have the length 21cm.