Question

The
perimeter of a triangle is 24cm two of its sides are 8cm and 9cm find the length of its third side

Answer 1

perimeter of triangle = s+s+s
24=8+9+x
24=17+x
17+x=24
x=24-17
x=7cm
so the third side = 7cm

Answer 2

Hello,
are a, b, c the three sides of the triangle.
we have that:
P=a+b+c=24 and a=8, b=9 
we calculate the third side:
c=P-a-b=24-8-9=7 cm

the thirs side measures 7 cm.

bye :-)