Help!!! How to find the dimensions on a house after its built if it is 18 feet by 16 feet. The only info they give me is that 1/2 in = 10 feet?? What formula do I use?

You can use a proportion. Cross multiply and solve for L (length).

(1/2)/10 = L/18
10L = 9
L = 9/10 inch

Figure the width on the blueprint the same way that I found the length.