Algebra - Substitution

"Substitute" means to put in the place of another.

Substitution

In Algebra "Substitution" means putting numbers where the letters are:

If you have:

And you know that x=6 ...

... then you can "substitute" 6 for x:

Example 1: If x=5 and y=3, then what is 10/x + 2y ?

Put "5" where "x" is, and "3" where "y" is: 10/5 + 2×3 = 2 + 6 = 8

Example 2: If x=3 and y=4, then what is x² + xy ?

Put "3" where "x" is, and "4" where "y" is: 3² + 3×4 = 9 + 12 = 21

Example 3: If x=3 (but you don't know "y"), then what is x² + xy ?

Put "3" where "x" is: 3² + 3y = 9 + 3y (that is as far as you can get)

As that last example showed, you may not always get a number for an answer, sometimes just a simpler formula.