The perimeter of triangle DEF is 81 units. The length of side DE is twice the length of side EF, and the side of DF is 4 units less than the side DE. What equation can be used to find EF where S is the lenght variable?

x + 2x + (2x - 4) = 81

And x (side EF) was found out to be 17 units

Step-by-step explanation:

The perimeter of a triangle is a+b+c where a, b and c are the side lenghts of the triangle.

The question here says that side DE is twice the lenght if side EF.

Now let's assume that the length of side EF to be x, then the side DE will be 2x.

And the length of side DF is 4 units less than the lenght o side DE.

this means that side DF = 2X - 4

Remember that the perimeter is 81 units

In this case,

x + 2x + (2x - 4) = 81 is the equation that we will use to derive the various lenghts of the triangle

Side EF which x will be

X + 2x + (2x - 4) = 81

5x - 4 = 81

5x = 85

X = 17

Therefore side EF which Is x = 17