Curriculum › Math ›Grade 6

Grade 6 Math · Level 3, Expressions, Equations & Inequalities

Advanced Linear Equations & Word Problems

How the lesson starts: Advanced Linear Equations & Word Problems

1. Rio's star crates

   Blast off to the Moon Arcade! Astronaut Rio has 3 crates with x stars in each, plus 5 loose stars. That's 20 stars in all: 3x + 5 = 20. Two things happened to x, so we'll need two undo steps. Let's crack it!

2. Undo in reverse

   Think of socks and shoes: socks go on first, but shoes come off first! In 3x + 5 = 20, x was multiplied by 3, then 5 was added. So undo the adding first: take 5 stars off both sides. 3x = 15. Then split into 3 groups: x = 5.

3. Let's work one out

   Now 2(x + 4) = 18. Two equal bags, each with x + 4 stars. Divide both sides by 2: each bag is x + 4 = 9. Then subtract 4: x = 5. Check: 2(5 + 4) = 2 × 9 = 18. Watch out: 2x + 4 forgets to double the 4!