To solve the equations provided, let's break them down one at a time.

1. **Equation 1:** \( 2x - 12 = 3 \)

To solve for \( x \), add 12 to both sides:

\[
2x = 3 + 12
\]
\[
2x = 15
\]

Now, divide both sides by 2:

\[
x = \frac{15}{2}
\]
\[
x = 7.5
\]

2. **Equation 2:** \( 42x - 12 = 3 \times 4 \)

First, simplify the right side:

\[
42x - 12 = 12
\]

Now, add 12 to both sides:

\[
42x = 12 + 12
\]
\[
42x = 24
\]

Next, divide both sides by 42:

\[
x = \frac{24}{42}
\]
\[
x = \frac{4}{7} \quad (\text{after simplifying})
\]

### Solutions:

1. For the first equation, \( x = 7.5 \).
2. For the second equation, \( x = \frac{4}{7} \).