Question

to find what number 12 is 30% of, use a 10-by-10 grid.
first, shade the 10-by-10 grid to show 30% of the entire grid.
select the cells to shade 30%.

Explanation:

Step1: Calculate total grid cells

A 10-by-10 grid has $10 \times 10 = 100$ total cells.

Step2: Find 30% of total cells

$30\% \times 100 = 0.30 \times 100 = 30$

Step3: Shade the calculated cells

Select any 30 individual cells in the 10-by-10 grid to shade (e.g., 3 full rows, since each row has 10 cells, $3 \times 10 = 30$).

Answer:

Shade 30 cells in the 10-by-10 grid (for example, the first 3 complete rows, or any combination of 30 individual cells). Additionally, to solve the original question "what number 12 is 30% of":

Step1: Set up percentage equation

Let $x$ = the unknown number. $30\% \times x = 12$ or $0.30x = 12$

Step2: Solve for $x$

$x = \frac{12}{0.30} = 40$

Final answer for the percentage question: $\boldsymbol{40}$; for the grid task: shade 30 cells.