4+6-3÷7 how do i get 1 for the answer

To get one for the answer, add parentheses around the terms (4+6-3)

(4+6-3)/7
7/7
1

P = side 1 +side 2 +side 3 

5x^3 +4x^2 -x -3 = 3x^2 -2x -1 + 9x +2x^2 -3 + 3rd side 

3rd side = P - (side 1 +side 2)

3rd side = 5x^3 +4x^2 -x -3 -(3x^2 -2x -1 +9x +2x^2 -3)

3rd side = 5x^3 +4x^2 -x -3 -5x^2 -7x +4

3rd side = 5x^3 -x^2 -8x +1

so the total length of the given two sides is equal 5x^2 +7x -4