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Hey there! Today we are going to learn how to use secret code words in math to solve fun puzzles.
Imagine you have a mystery gift box. You don't know how many candies are inside yet, so we can use a letter like 'x' to stand for that secret number! In math, we call this letter a variable because its value can vary or change.
An algebraic expression is like a math phrase. If we have our mystery box 'x' and we add 3 more candies next to it, we write this as 'x + 3'. Watch how the variable and the number join together to make an expression!
What if we find out the mystery box 'x' actually has 5 candies inside? We can replace, or substitute, the 'x' with the number 5. Then our expression 'x + 3' becomes '5 + 3', which equals 8!
Evaluate the expression 'y - 4' when y = 10.
- Identify the variable in the expression, which is 'y'.
- Look at the given value for the variable: y = 10.
- Substitute (replace) 'y' with the number 10 in the expression.
- Rewrite the expression as '10 - 4'.
- Subtract 4 from 10 to get the final answer: 6!
