12 7/23 -(6 18/23 -t) = 3 21/23 + 5 19/23
12 7/23 -(6 18/23 -t) = 8 40/23
6 18/23 -t = 12 7/23-8 40/23
6 18/23 -t = 10 53/23-8 40/23
6 18/23 -t = 2 13/23
t=6 18/23 - 2 13/23
t=4 5/23
12 7/23 -(6 18/23 -t) = 3 21/23 + 5 19/23
12 7/23 -(6 18/23 -t) = 8 40/23
6 18/23 -t = 12 7/23-8 40/23
6 18/23 -t = 10 53/23-8 40/23
6 18/23 -t = 2 13/23
t=6 18/23 - 2 13/23
t=4 5/23