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 — Use an equal sign to show two sides match.
• Equation — A math sentence with an equal sign.
• Variable — A letter that stands for a number.
• Equal sign — The = sign. Both sides are the same.
• Expression — A math phrase. It has no equal sign.
• Constant — A number that stays the same.
• Unknown — The value you want to find.
• Solution — A value that makes the math sentence true.
• Substitute — Put a number in place of a letter.
• Estimate — An answer that is close, found without exact work.

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 k + 7 = 15, and how do you know?

Check your answer

k = 8, because 8 + 7 = 15 is true

Substitute each value and check. Replacing k with 8 gives 8 + 7 = 15, a true statement, so 8 is the solution.

Sentence starter

I know ___ because ___.

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