65 is 13% of what number

24

Step-by-step explanation:

24 just do the math

Perimeter:
 The perimeter of the triangle is the sum of its sides.
 We have then:
 P = 8 + 12 + 10
 P = 30 units

 Semi-perimeter: 
 In geometry, the semiperimeter of a polygon is half its perimeter.
 s = P / 2
 s = 30/2
 s = 15 units.

 Area: 
 Knowing the semiperimeter and the sides, the area is:
 A = root (s * (s-a) * (s-b) * (s-c))
 where,
 s: semi-meter
 a, b, c are sides.
 A = root (15 * (15-8) * (15-12) * (15-10))
 A = 39.68626967
 A = 40 units ^ 2