Question 836172
1/j+1/f=1/6,
1/t+1/j=1/7.5,
1/t+1/f=1/10
f = 15,   j = 10,   t = 30
check
1/10+1/15=1/6
3/30+2/30=1/6
5/30=1/6
ok
1/10+1/30=1/7.5
3/30+1/30=1/7.5
4/30=1/7.5
ok
1/30+1/15=1/10
1/30+2/30=1/10
3/30=1/10
ok