Lesson 1: Understand Equations and Their Solutions6.AT.8

I can…

I can write an equation for a real situation and check whether a given value is a solution by substituting it.

Key words

• Write Equations — Represent a relationship with expressions joined by an equal sign.
• Equation — A math sentence with an equal sign showing both sides are the same.
• Variable — A letter that stands for a number that is unknown or can change.
• Equal sign — The = sign, showing both sides are the same.
• Expression — A math phrase with numbers and letters, but no equal sign.
• Constant — A fixed number in an expression or equation that does not change.
• Unknown — The value you are trying to find, usually shown with a variable.
• Solution — A value that makes an equation true when it is substituted for the variable.
• Substitute — To replace a variable with a number so the equation can be checked.

Steps

1. Clue: 'A number of stolen gems plus 8 more equals 20 total.'
2. The unknown is the number of gems. I let n stand for it.
3. 'Plus 8 more' means + 8. 'Equals 20 total' means = 20.
4. So my equation is n + 8 = 20.

Try it

Which value is the solution of n + 5 = 9, and how do you know?

Check your answer

n = 4, because 4 + 5 = 9 is true

Substitute each value and check. Replacing n with 4 gives 4 + 5 = 9, a true statement, so 4 is the solution.

Sentence starter

I know ___ because ___.

Goal: I can explain a solution using the words substitute, solution, true, and equal sign.