15 points the surface area of a cone with radius r units and slant height s units is shown below: surface area = 3.14(rs + r2) part a: if r = 6 units and s = 4 units, write an expression that can be used to calculate the surface area of the cone. (4 points) part b: what is the surface area of the cone? show your work. (6 points)

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.