Not sure how to do this.

200π

Step-by-step explanation:

Surface area is abbreviated to SA

TOTAL SA of cone = Base area + πrl

Base area = πr² = π x 8² = 64π

Curved SA = πrl = π x 8 x l

to work out l, use pythagoras theorem: √(15)² + (8)² = 17

so, curved SA = π x 8 x 17 = 136π

Total SA of cone = 64π + 136π = 200π

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional