What is Sudoku? Answer it

Sudoku is a logic-based, combinatorial number-placement puzzle.

Explanation: In classic sudoku, the objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids that compose the grid contain all of the digits from 1 to 9. The 18th century Swiss mathematician Leonhard Eulu apparently developed the concept of a “Latin square” , where a number in a grid appears only once, across, up and down. Dell Magazine in the US began publishing in the 1970s what is now known as Sudoku. It was developed by an independent puzzle maker, Howard Games.

if triangle abc is congruent to triangle def, their interior angles are congruent, because congruent parts of congruent triangles are congruent (cpctc).

that means ∠d is congruent to ∠a; ∠d is equal to 8x - 2.

interior angles of all triangles add to equal 180 degrees, so you can set the sum of these interior angle values equal to 180 and solve for x.

180 = (8x - 2) + 22 + 72

180 = 8x - 2 + 22 + 72

180 = 8x + 92

88 = 8x

11 = x

x = 11