The second step is to keep your x terms on the left and move the constant to the right by subtracting it from both sides.
Answer:
<em>T </em><em>=</em><em> </em><em>1</em><em>6</em>
Step-by-step explanation:
As triangles are similar
AB/DE = BC/EF = AC/DF
13.5/18 = 6/4 = 12/T
3/4 = 3/4 = 12/T
3/4 = 12/T
T = 12×4/3
T = 16
Just remember it's along the corridor and up the stairs so horizontal comes first