Question

Which could be the first step in solving the equation represented by the model below?

Add 4 positive unit tiles to each side.
Remove 4 unit tiles from each side.
Add 6 positive unit tiles to each side.
Remove 6 unit tiles from each side.

Answer 1

The answer is A. Add 4 positive unit tiles to each side.

Answer 2

Add 4 positive unit tiles to each side.

Explanation:

The original equation is:

3x - 4 = 2x + 5

After adding 4 positive unit tiles to each side, we get:

3x - 4 + 4 = 2x + 5 + 4

3x = 2x + 9

which simplifies the original equation, because at the beginning there were independent terms at both sides of the equal sign and now all independent terms are on the right side (the +9 term). Notice that the other options don't give this result.