Answer:
2. Denote two pieces: x, y
x + y = 40
x = 2y + 10
=> 2y + 10 + y = 40 => 3y = 30 => y = 10 => x = 2 x 10 + 10 = 30
=> Solution: 10 and 30
3. Denote 4 consecutive number: 2k, 2k+2, 2k+4, 2k+6
(2k + 2k + 4) x 2 + 20 = 2 x (2k + 6)
=> 8k + 28 = 4k + 12
=> 4k = -16
=> k = -4
=> Solution: -8, -6, -4, -2
4. The number of shoppers after announcement :
N = 320 x 150/100 = 480
Hope this helps!
:)
