The first problem to be solved is the answer to the problem on page 176 of mathematics volume 1 of Grade 7 in Beijing Normal University

The first problem to be solved is the answer to the problem on page 176 of mathematics volume 1 of Grade 7 in Beijing Normal University

If one digit is x, then ten digit is [10 * (2x)]
According to the meaning of the question, the equation can be listed as follows: (20x + x) - (10x + 2x) = 36
21X-12X=36
9X=36
X=4
Two digit = [10 * (2x)] + x = 10 * 2 * 4 + 4 = 80 + 4 = 84