Before 1. 10, the father's age was six times that of his son, and after 10, the father's age was twice that of his son. Q: How old are father and son this year?

Solutions; Suppose 10 years later, the age of the son is x and the age of the father is 2x.

(2x-20)=6(x-20)

2x-20=6x- 120

4x= 100

x=25

Son this year: 25- 10= 15 (years old)

Father this year; 2x25- 10=40 (years old)

2. Choose five students from each class in the sixth grade of experimental middle school to form a team and have a math contest. The rules of the contest are: each pair will give 50 questions respectively, get 3 points for answering one question correctly, and deduct 1 point for failing to answer or answering one question incorrectly. If the final score of the representative of Class Three is 142, how many questions did the representative of Class Three answer correctly?

50x3= 150 (minimum)

150- 142=8 (point)

Wrong answer: 8/(3+ 1)=2 (Dao)

Correct answer: 50-2=48 (Dao)

3. Last year, Factory A and Factory B completed 120% and 1 10% of the planned tasks respectively, and * * * produced 4,000 tons of grain, 400 tons more than the planned sum of the original two factories. What is the initial production task of Factory A?

A120%+b110% = 4000 (ton)

A 20%+ B 10%=400 (ton)

A 120%+ B 60%=2400 (ton)

B: (4000-2400)x2=3200 (ton)

A: (400-3200x 10%)/(20%)=400 (ton).