Question

The perimeter of a triangle is 7x 3y + 10 and two of its sides are x - 2y +1 and 3x - 5y +3. Find the third side.​

Answer 1

perimeter of a triangle is the sum of its 3 sides

here,

perimeter = 7x - 3y + 10

two sides = x-2y+1  , 3x-5y+3

third side = ( 7x - 3y+10 ) - ((x-2y+1)+(3x-5y+3))

               = ( 7x - 3y+10 ) - (x-2y+1+3x-5y+3)

               = ( 7x - 3y+10 ) - ( 4x -7y +4 )

               =  7x - 3y+10 - 4x +7y - 4

third side  = 3x + 4y +6

hope this helps..