Theresa has two brothers, paul and steve, who are both the same height. paul says he is 16 inches shorter than 1 1/2 times theresa's height. steve says he's 6 inches shorter than 1 1/3 times theresa's height. if they're both right, how tall is theresa ?

Let 
x> Paul and Steve heights
y> Theresa height

we know that
1 1/2> 3/2---> 1.5
1 1/3> 4/3> 1.33
 Paul says he is 16 inches shorter than 1 1/2 times Theresa's height
x=1.5y-16> equation 1

Steve says he's 6 inches shorter than 1 1/3 times Theresa's height
x=1.33y-6> equation 2

equals 1 and 2
1.5y-16=1.33y-6
1.5y-1.33y=-6+16
0.17y=10> y=58.82 in

x=1.5y-16> 1.5*(58.82)-16> x=72.24 in

the answer is
Theresa is 58.82 in tall