Algebra is used to find a missing number in an equation. The number is replaced with a letter (for example "x") sometimes multiplied by another number (for example "3x".) You need to rearrange the numbers in the equation to find the numeric value of the letter. You should do this in stages moving one part of the sum at a time so eventually the letter is on one side of the equation on its own.

Read the equation. Find the letter that you are supposed to be finding the numeric value of. For example 3x/7+8 =25. You are trying to find the value of "x."

Perform the first sum of the equation to start shifting the numbers to one side of it. For example for 3x/7+8 =25 the first number we would like to move across is the "8." To move a number preceded by "+" we must subtract it from the number on the opposite side of the equation. So 25-8= 17. The equation now reads 3x/7= 17.

Move the next number to the other side of the equation. In the example case where the equation now reads 3x/7= 17 you need to move the "7" across. As the number on that side of the equation is being divided we need to multiple the number on the opposite side to pass the number across. So 17 X 7= 119. The equation now reads 3x = 119.

Make the multiple of the letter into a single value. In the example case of 3x=119, we want to make "3x" into "x." 119 needs to be divided by 3 to find the single value of "x." So 119/3 = 39.6666666.