This leaves us a more manageable equation, 4 * 2 + 6 = x + 2 (remember that * means multiply). After simplifying things a little we get 14 = x + 2. Subtract 2 from each side and you'll discover that x = 12.

Substitution can also involve more complicated problems, like 5x^2 + 2y -6 = y, where y = -1 and x = 4. Just substitute in the same way, placing the value of each variable in place of the letter and simplifying.

There is another form of substitution. This is where we insert a variable to stand for a particular expression. In some cases you will be dealing with incredibly complex problems, and it may be easier to substitute a variable, like y for part of the problem. Then, when you have solved the value of y, you can plug back in the original expression.