Spiders have eight feet, dragonflies have six feet and two pairs of wings, and flies have six feet and 1 pairs of wings. Insects have three kinds of *** 18, * * * have 1 18 feet and 20 pairs of wings. Q: How many insects are there in each species? Formula: (8×18-118) ÷ (8-6) =13 (only) 18- 13=5 (only). 1 18-8×5=78 (only) (20-13×1) ÷ (2-1) = 7 (only) Analysis: (8×/kloc) Divided by (8-6) is the number of feet that spiders have more than dragonflies, and the number obtained is only the number of dragonflies and spiders.

18- 13 to get the number of spiders, 18-5×8 to get the number of feet except spiders, dragonflies and flies.

(20- 13× 1) means that all 20 pairs of wings are flies, and the extra wings are dragonflies, while ÷(2- 1) is the logarithm of dragonfly wings more than flies, giving the number of dragonflies, and 13-7 gives the number of flies.

There are seven numbers, and their average value is 18. After removing one number, the average value of the remaining six numbers is19; After removing another number, the average of the remaining five numbers is 20. Find the product of two numbers. Formula: 7×18-6×19 =126-114 =12.

6 *19-5 * 20 = 14-100 =14 Analysis: The two numbers removed are 12 and14, and their product is14.

3. When Party A and Party B participate in the knowledge contest, each correct answer gets 20 points, each wrong answer gets 12 points, each question gets 10 points, and * * * gets 208 points, of which Party A gets 64 points more than Party B. How many questions did Party A and Party B do correctly? Formula: b score (208-64)/2=72.

One point is 208-72= 136.

An error (20 *10-136)/(20+12) = 2.

A pair of 10-2=8

Wrong b (20 *10-72)/(20+12) = 4.

B pair 10-4=6

A answers 8 questions correctly and B answers 6 questions correctly.

There are 77 workers in a workshop, and it is known that each worker can process 5 A, 4 B or 3 C pieces on average every day. However, processing three A-type parts, one B-type part and nine C-type parts is just one set. How many workers do you need to arrange for each of the three parts A, B and C, so that all the three parts A, B and C can be assembled? Formula: This problem can be solved by equation: Solution: Suppose B has X parts after processing.

3/5X + 1/4X + 9/3X=77

x=20

A: 0.6×20= 12 (person) B: 0.25×20=5 (person) C: 3×20==60 (person).

A: There are 12 people in Party A, 5 people in Party B and 60 people in Party C. ..

My brother is three times as old as his brother. My brother is the same age as his brother. The elder brother and younger brother are 30 years old. How old are the younger brothers and younger brothers? Equation: This problem can be solved by equation: Solution: Suppose my brother is now X years old.

x-(30-x)=(30-x)-x/3

x= 18

Brother 30- 18= 12 (years old)

A: My brother 18 years old, and my brother 12 years old.

It's already a lot. Hope to adopt.