PLease help me with this math qestion

n+3 = 15 ; n = 12

3n -6 = 12;  n=6

Step-by-step explanation:

more than means it comes after

a number

n

3 more than

n+3

is 15

n+3 = 15

Subtract 3 from each side

n+3-3 = 15-3

n = 12

Subtract from comes after

three times a number

3n  

six subtracted from

3n -6

is 12 means equal to

3n -6 = 12

To solve add 6 to each side

3n -6+6 =12+6

3n = 18

Divide by 3

3n/3 =18/3

n =6

what is the total surface area of the compound shape if it diameter is 24cm, if it slant height of the cone is 13cm and the height of the cylinder alone is thrice that of the cone alone.