# Exactly Three-quarters

##### Stage: 3 Short Challenge Level:

The area of the rectangle is $48cm^2$, so the unshaded area is $12cm^2$. Therefore taking the two unshaded triangles together: ($1/2\times x\times2$) + ($1/2\times(6-x)\times8$) $= 12$ which means that $x + 24 - 4x = 12$, so $x = 4$.

This problem is taken from the UKMT Mathematical Challenges.