Answer:
143 inches
Step-by-step explanation:
Let the triangle be [tex]s[/tex] inches long.
Then the perimeter of the equilateral triangle will be [tex]s+s+s=3s[/tex] inches.
Let the length of the square also be [tex]l[/tex] inches.
Then the perimeter is [tex]4l[/tex]
It was given that the perimeter of the equilateral triangle is 77 inches more than the perimeter of the square.
So we can write the relation
[tex]3s=4l+77[/tex]
[tex]\Rightarrow 3s-4l=77..eqn1[/tex]
Also, the side of the triangle is 55 inches longer than the side of the square.
So we write [tex]s=l+55[/tex] or [tex]l=s-55...eqn2[/tex]
We put equation (2) into equation (1) to get;
[tex]3s-4(s-55)=77[/tex]
We expand the bracket to get;
[tex]3s-4s+220=77[/tex]
[tex]3s-4s=77-220[/tex]
[tex]-s=-143[/tex]
[tex]s=143[/tex]
Hence the triangle is 143 inches long.