6less than a number is 15. let x represent the number. which equation represents this?
a. 15 - x = 6
b. x + 6 = 15
c. 6 - x = 15
d. x - 6 = 15

**Note / Protip**
Always substitute "a number" for your variable when reading worded equations!
With that being said...

D. x - 6 = 15

Is your answer, since you are going to want to reverse it because of how the problem's worded, not c. because; c.'s worded equation would be
"A number less than six."

10.26 bags

Step-by-step explanation:

Area of circle :

A = πr²

radius, r = 7ft

A = π * 7²

A = π * 49

A = 153.93804 ft²

Since a bag covers 15 ft² ;

Number of bags needed will be :

Area / number of square feet per bag

153.93804 ft² / 15 ft²

= 10.262536 bags

= 10.26 bags