3) \( 12+z=15 \)

To solve the equation \( 12 + z = 15 \), you simply need to isolate \( z \). Subtract 12 from both sides of the equation: \( z = 15 - 12 \). Therefore, \( z = 3 \)! Simple as pie! This equation is a classic example of how we can use algebra to flex our problem-solving muscles! Real-life applications of such equations are everywhere, from budgeting your money to calculating distances. When you know how to manipulate basic equations, you can tackle a variety of everyday problems with ease!