The teacher gave two questions, and 42 students in the class did 28 questions in the first question, and 2 1 person in the second question, 10 person made a mistake. How many people in the class did it right? The teacher gave two questions, 42 students in the class did 265,438+0 on the first question, and the wrong question was 10, and the class was 27.

According to the meaning of the question, suppose that X people only got the first question right, Y people only got the second question right, and Z people got everything right.

Equations:

x+y+z=32

x+z=28

y+z=2 1

Solution: x= 1 1, y=4, z= 17.

So okay * * * There are 17 people.

Steps to solve the equation:

① Using substitution method or addition and subtraction method, an unknown number is eliminated, and a set of binary linear equations is obtained.

(2) Solve the binary linear equations and get two unknown values.

(3) Substitute the values of these two unknowns into a simple equation in the original equation, find the value of the third unknown, and write these three numbers together to get the solution of the ternary linear equations.