Problem
㉠ (left 8, top 6) mirrors across the fold to left 6, top 8, whose cell holds 6 x 8 = 48.
Folding swaps the two heads of a cell, and a x b equals b x a, so the meeting cell shows the same product.
3.OA.B.5Draw A DiagramThe cell that lands on ㉠ when the table is folded holds the very same number as ㉠.
The fold lays ㉠, at left 8 and top 6, exactly onto the cell at left 6 and top 8, so those two cells are the pair that meets.
The fold line is the diagonal where the left number equals the top number, and folding lays one half of the table exactly onto the other half, so the cell that is 8 down and 6 across matches the cell that is 6 down and 8 across.
The meeting cell at left 6 and top 8 holds 6 times 8, ㉠ holds 8 times 6, and those two products are equal.
Swapping the two numbers being multiplied does not change the product, so 6 times 8 and 8 times 6 are the same number.
㉡ (left 6, top 7) mirrors across the fold to left 7, top 6, whose cell holds 7 x 6 = 42.
Same idea: swapping the heads keeps the product, so the mirror cell is also 42.
3.OA.B.5Look For A PatternThe ㉠ cell holds 48 and the ㉡ cell holds 42, so the sum is 48 + 42 = 90.
Once both meeting values are known, the answer is a simple addition.
3.OA.C.7Draw A DiagramFolding the table just swaps the row and column numbers, and since 6x8 = 8x6, the mirror cell shows the very same product!