Well, their speeds are (

is Jack's speed, and

is Richard's.

They, together, can paint 12 houses in 35 days. To get a single house, we only have to calculate

which is very close to 3 (a bit below)
Answer:
A is the answer
Step-by-step explanation:
3×3 is 9 and 2×3 is 6

Actually Welcome to the Concept of the volumes.
Here given as, r= 6.2 mm, h = 10.8 mm, π=3.14
hence, the volume of the cone is
Volume = 1/3(πr^2h)
===> vol = 1/3(3.14*(6.2)^2*(10.8))
==> Vol = 1/3*(1303.57)
==> Vol = 434.52 mm^3
Hence the volume of the cone is 434.52 mm^3
-4.666666(so forth) or -4.7 if the problem requires you to round.