Step-by-step explanation:
Use properties of similar triangles.

There you are!
:)
Your answer is most likely B
one ounce is too small
five pounds is too large
and four pounds seems like it wouldn't be accurate enough
4x-3=12
add 3
4x=15
divide 4
x=15/4
x=12/4+3/4
x=3+3/4
x=3 and 3/4
answer is 3 and 3/4