3-6:4*7

To solve the expression \(3 - 6:4 \times 7\), we first need to clarify the operations involved. The colon (:) typically denotes division, so we can rewrite it as:

\[ 3 - \frac{6}{4} \times 7 \]

Now, we will follow the order of operations (PEMDAS/BODMAS):

1. Division: \(\frac{6}{4} = 1.5\)
2. Multiplication: \(1.5 \times 7 = 10.5\)
3. Subtraction: \(3 - 10.5 = -7.5\)

So, the final answer is:

\(-7.5\)