Here are the answers using the substitution technique:

For the equations:

1. $x + 2y = 12$
2. $3x - y = 7$

Solution:

• $x = \frac{26}{7}$
• $y = \frac{29}{7}$

Would you like any further assistance or additional questions? Here are some related queries:

1. How do you use substitution to solve equations with fractions?
2. Can you solve these equations using the elimination method?
3. Would you like help with a different set of simultaneous equations?
4. Are there any tips for solving equations with more complex coefficients?
5. How can you verify if your solution is correct?

Tip: Always simplify the equations as much as possible before substituting to make calculations easier.