Use the order of operations to evaluate the expression.

First, we need to solve the parentheses:

3/4 - 1/2 = 3/4 - 2/4 = 1/4

Now the expression becomes:

4 * (1/4) + 3 * 6

Next, we calculate the multiplication:

4 * (1/4) = 1

So the expression now becomes:

1 + 3 * 6

Now we multiply:

3 * 6 = 18

Finally, we add:

1 + 18 = 19

Therefore, the answer is A. 19.