快快快!!math,要例式and答案(有10分)

Question

1.20 minus the product of a number and 2 is equal to the square of 4.find the number
2.the sum of three consecutive even number is 42.find the three numbers.
3.the sum of three consecutive odd number is 81 find the three number.

Answer 1

1.
Let the number be x
20 - 2x = 4 ^ 2
20 - 2x = 16
-2x = -4
x = 2

2.
Let the smallest number be x
x + (x + 2) + (x + 4) = 42
3x + 6 = 42
3x = 36
x = 12
The three numbers are 12 , 14 , 16

3.
let the smallest number be x ,
x + (x + 2) + ( x + 4) = 81
3x + 6 = 81
3x = 75
x = 25

The three numbers are 25 , 27 , 29

Answer 2

1. Let x be the number
20-2x=4^2
20-2x=16
4=2x
x=2

2.Let x be the smallest number
(x)+(x+2)+(x+4)=42
3x+6=42
3x=36
x=12
~ These numbers are even
~ the numbers are 12,14,16