Perimeter of a triangle is the sum of measures of its all three sides, let the other be y,
we know,
[tex] \hookrightarrow \: y + 3x + 2 + 4x - 9 = 16x - 6[/tex]
[tex] \hookrightarrow \: y + 7x - 7 = 16x - 6[/tex]
[tex] \hookrightarrow \: y = 16x - 6 - 7x + 7[/tex]
[tex] \hookrightarrow \: y = 6x + 1[/tex]
hence, measure of the third side is 6x + 1
