In certain equations, the student may know to plug in the amounts for the variables. Variables are the letters which stand for a certain number. Each different variable stands for a different variable. Sometimes, in equations there are ways to find out the variable amount by moving parts of the equation to the other side of the equal side or combining like terms.
There may also be times when problems explain what the variable may or may not be equivalent to based upon sentences given to the student. In most cases, the problem should be solved by finding the amount for the variable, but sometimes the answer may not be in the form of a number. In this case the variable z stands for 50.