Two sides of a triangle are equal in length. the length of the third side is three meters less than the sum of the lengths of the other two sides. find the length of the longest side of the triangle if it's perimeter is 29 meters.

We have an isosceles triangle: 
The length of the sides are:
side₁=side₂=x
side₃=(x+x)-3=2x-3
Perimeter of a triangle=is the sum of the all sides.

we have this equation:
x+x+(2x-3)=29
4x=29+3
4x=32
x=32/4
x=8

The length of the third triangle will be: 2x-3=2*8-3=16-3=13

The length of the longest side of the triangle would be 13 meters.