we know that
Perimeter of a triangle is equal to
P=a+b+c
where
a,b and c are the length sides of the triangle
Find the perimeter of the triangles
Triangle N 1
P=(x-2)+(x)+(3x+1)-------> P=5x-1
Triangle N 2
P=(2x-5)+(x+4)+(6x-7)------> P=9x-8
equate the perimeters
5x-1=9x-8--------> 9x-5x=-1+8-------> 4x=7
x=7/4------> x=1.75
therefore
the answer is
x=1.75