If 6 drums of oil will heat 5 buildings for 3 days, how many days will 10 drums of oil last when heating 2 buildings?

Is it 12.5 days?

oil = k(number of buildings)(number of days)

o = k bd
given: o=6, b=5, d=3
6 = k(15)
k = 6/15 = 2/5

oil = (2/5)(bd)
10 = (2/5)(2d)
d = 50/4 = 12.5

I agree