Refraction, how tall is the image?

[Quantum Joe]

Homework Statement

If the object distance in the following picture were 8.0 m and the image distance were 2.0 m, and the object is 0.50 m tall, how tall is the image.

H_o = 0.5
S_o = 2.0
S_i = 8.0

Homework Equations

H_o / H_i = S_o / -S_i
In order these variables are height object, height image, object distance and object image.

The Attempt at a Solution

0.5/ H_i = 2.0/8.0

This is where the problem occurs. How do I get H_i on one side of the equation?

I don't know how to move the numerator to the other side of the equation... Please help... I think there is a very simple solution but, it is eluding me.

 

[Delphi51]

Where did the minus sign go?
Cross multiply to eliminate all fractions:
0.5*8.0 = 2.0*Hi