Let x be the common length. Then, the sides of the triangle are x, x, and 2x-6. These three sides sum up to 22, so you have
[tex] x+x+2x-6 = 22 \iff 4x = 28 \iff x = 7 [/tex]
So, the two equal sides are 7m long, and the third side is
[tex] 2\cdot 7 - 6 = 14 - 6 = 8 [/tex]