Question

see question no 6 and answer

Answer 1

perimeter = sum of all the three sides
          36  = 12+14+x
x = 36 - 24 = 10 cm

Answer 2

we know that
the perimeter of triangle= sum of all side
36=12+14+x
36=26+x
x=36-26
x=10
the third side of triangle is 10cm