Anser is B). Subtract smallest number
The answer would be C (P=T/2). This can be explained by examining the ratio. If you were to put in the answer of T = 12, then you would be looking for T/2 or 6, assuming we're giving them each half of the amount original held by grandmother.
A+30 = 60
a = 30
a + 2b = 60
30+2b = 60
2b = 30
b = 15
5b - 5c = 60
5(15) - 5c = 60
5c = 15
c = 3
10c + d = 60
10(3) + d = 60
30 + d = 60
d = 30
2d + 6e = 180 - 60
2(30) + 6e = 120
6e = 60
e = 10
4f + 4e = 120
4f + 4(10) = 120
4f = 80
f = 20