deriving an equation

[Brit412]

1. The problem statement, all variables and given/known data
Using equations #1 and #2 to derive equation #3

2. Relevant equations
#1- ∆x = (b/2)theta
#2- ∆z= L (2theta)
#3- ∆x= ∆z b/4L


3. The attempt at a solution
Now I set equations #1 and #2 equal to each other, but I'm not sure how the thetas end up cancelling or if I'm even supposed to set them equal to each other in the first place. HELP please!!

[borgwal]

Just divide one equation by the other.

[Brit412]

Does that mean that I divide (b/2)theta by L(2theta)?

[borgwal]

Yes, you divide the right-hand sides of the two equations, and the result must equal the ratio of the left-hand sides of the same two equations.