Method 1 (logical thinking method) (reflecting the wisdom of China people)
Assuming that Xiao Ming answers all the questions correctly, Xiao Ming's score is: 20*8= 160, while Er Xiaoming's actual score is 134. Assuming that the situation is different from the actual situation: 160- 134=26, there must be some mistakes in those twenty questions. At present, it is assumed that 20 questions are all right, and a correct question is not only missing one (that is, 8 points less), but also adding one more wrong question (5 points should be deducted backwards). As a result, one correct question was less than the original one (5+8= 13), and now it is actually less than 26 points, which means there are actually 20 questions.
Method 2 (Solving Equation) (Western Thinking)
Suppose Xiaoming is on track X and off track (20-x).
8x-5*(20-x)= 134，
The solution is x= 18.
Hehe, I hope it will help you!