The value of x from the missing side of the given equilateral and isosceles triangles would be = 7
How to calculate the missing value of the given triangle?
From the definition of an equilateral triangle, the three sides of the triangle are said to be equal.
Therefore,
3x-5 = 5y-4= y+12
Using;
5y-4 = y+12
Bring like terms together;
5y-y = 12+4
4y = 16
y = 16/4 = 4
But;
3x-5 = (4)+12
3x -5 = 16
3x = 16+5
= 21
X = 21/3
= 7