Middle school · Linear equations
Solve while keeping both sides equal
Remove the same constant from both sides, then divide equal groups to reveal x.
Predict what will happen, press Play, then pause and explain what changed. Every control also works without playback.
Watch the relationship
PausedHD animation studio
From experiment to screen.
Present a crisp Canvas scene, save a full-HD image, or capture your model as a silent video.
Understand what you are seeing
The idea behind the motion.
An equation is a statement of equal values. Subtracting the same number from both sides preserves that statement. When several identical x-boxes remain, dividing both sides by the same nonzero number isolates one box. Substitution checks that the result still satisfies the original equation.
A relationship to keep
ax + b = c → ax = c − b → x = (c − b)/a
Read the symbols alongside the explanation. A diagram shows the relationship; the assumptions tell you when it applies.
- STEP 1
Create a balanced equation
Choose the hidden value, the number of identical boxes, and the added constant. The right-hand total is calculated to make the original equation true.
- STEP 2
Subtract on both sides
In the first half of the animation, equal constant tiles leave both pans together. At the halfway point, only the identical x-boxes and their combined value remain.
- STEP 3
Divide into equal shares
In the second half, the known total is separated into the same number of equal shares as there are boxes. At the end, one highlighted share identifies x. Multiply and add back to check the starting equation.
Your turn to explain
Make a prediction. Test your reasoning.
Solve 4x + 7 = 31. Which operation comes first, and what is x?
Use the values specified in the question. Reset restores the initial values for this investigation.
Compare your explanation
Subtract 7 from both sides to get 4x = 24. Then divide both sides by 4, giving x = 6. Check: 4 × 6 + 7 = 31.
Work through a full lesson
Connect the animation to a worked example and practice questions.