Solve the following system of equations using substitution.
u = 6 + t
36 = 2t + u
At = 10, u = 16
Bt = 10, u = 4
Ct = 14, u = 20
Dt = 16, u = 22
u = 6 + t
36 = 2t + u
At = 10, u = 16
Bt = 10, u = 4
Ct = 14, u = 20
Dt = 16, u = 22