(15) ? is this correct or am i missing something, : )

You are correct!

Step 1:Write what you know
Madeline's Height: 6 ftMadeline's Shadow: 108 in
Friend's Height: X (we use X as a variable because his height is unknown)Friend's Shadow: 108 in - 1.5 ft                              108 in - 18 in                                 90 in
Step 2:Set up proportions
6          x = 108      90 
Step 3:Cross Multiply & Solve
108x = 540x = 5 ft tall

Hope this ; )