Welcome to "Probe Expression Builder", a 6th Grade Expressions mission at the Challenger (stretch) level, staged in our space exploration scenario. The mission opens with a hands-on prompt: "Use algebra tiles to build the expression 15x + 18." You'll reason about the numbers 15, 18, 7 across 3 guided steps.
Behind the space exploration story, this lesson is really about expressions aligned to CCSS 6.EE.A.2. Write, read, and evaluate expressions in which letters stand for numbers. The key strategy this mission asks you to internalise: Answer: 123.
A general pattern to watch for in 6th Grade expressions — illustrated with example numbers below, which may differ from this lesson's: Reading "3x" as "3 plus x" instead of "3 times x". A coefficient next to a variable means MULTIPLY. 3x = 3 × x. If you get stuck on "Probe Expression Builder", the adaptive Socratic hints below escalate from a gentle nudge to a worked-out strategy — the same way a one-on-one tutor would coach you through it.
Grade 6 · Expressions
Mission Progress
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Thinking Summary · 1
Mastered[object Object]
[Discovery] Use algebra tiles to build the expression 15x + 18.
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Active StepBuild 15x + 18 using x-tiles and 1-tiles.
Everything you need to know about the Socratic experience.
Use algebra tiles to build the expression 15x + 18. Hint: Each x-tile counts as one x. Each 1-tile is a unit. You need 15 x-tiles and 18 1-tiles.
In the expression 15x + 18, what is the constant? If you get stuck, the adaptive hint is: Answer: 18.
Challenger missions push beyond CCSS expectations with edge cases that surface deeper misconceptions. Within 6th Grade Expressions, expect numbers in the corresponding range.
Translating "3 less than n" as "3 - n" instead of "n - 3". "Less than" REVERSES the order. "3 less than 10" = 10 - 3 = 7.
Equations (Equations come from setting expressions equal.). Open /grade-6/equations to start that topic's missions.
Yes. Every mission, handbook page, and topic hub is mapped to a specific CCSS code (visible in the page header). The curriculum follows the CCSS coherence map: Grade 1 number sense → Grade 3 multiplicative thinking → Grade 6 ratio reasoning, with each grade building strictly on the prior year's foundations.
Pure discovery is inefficient — kids hit a wall and quit. Guided Discovery scaffolds the path: a careful sequence of questions, models, and adaptive hints leads the learner toward the insight without revealing it. Inquiry AI's hint system fires automatically after ~15s of hesitation or on the first mistake, escalating from a Socratic nudge to a worked example only when needed. Mistakes are diagnosed via "misconception keys" so the hint matches the actual wrong-thinking pattern.
