Explanation:
P = height of Paul.
S = height of Steve.
t = height of Theresa.
P = 1 1/2 t - 16 = 3t/2 - 16
S = 1 1/3 t - 6 = 4t/3 - 6
because Paul and Steve have the same height, we can say
P = S
3t/2 - 16 = 4t/3 - 6
3t/2 - 10 = 4t/3
9t/2 - 30 = 4t
9t - 60 = 8t
t = 60
so,
Theresa is 60" tall.
Paul and Steve are 4×60/3 - 6 = 240/3 - 6 = 80 - 6 = 74" tall