Penjelasan dengan langkah-langkah:

1. -4#(-2)#9

(-4)² + (-2) - 5(9)

16 - 2 - 45

14 - 45

- 31.

2. 7 × 160 = 1.120 kg

1.120 - ⅝(1.120) = 1.120 - 700 = 420 kg

2½ = 2,5 kg

420/2,5 = 168 orang.

3. Angka pertama = x

Angka kedua = y

Angka ketiga = z

y = 3x

z = 4x

Maka :

x + y + z = 128

x + 3x + 4x = 128

8x = 128

x = 16.

y = 3x = 3 × 16 = 48.

z = 4x = 4 × 16 = 64.

16, 48, 64.

4. ⅜(2x - 4) = ¼(4x + 5)

3(2x - 4) = 2(4x + 5) (kedua ruas dikali 8)

6x - 12 = 8x + 10

- 12 - 10 = 8x - 6x

- 22 = 2x

x = - 11.

5. 2p + 2l = keliling persegi panjang.

Maka :

2p + 2l = 68

2(x + 3) + 2(3x - 5) = 68

2x + 6 + 6x - 10 = 68

8x - 4 = 68

8x = 68 + 4

8x = 72

x = 9.

p (panjang) = x + 3 = 9 + 3 = 12 cm.

l (lebar) = 3x - 5 = 3(9) - 5 = 27 - 5 = 22 cm.

Semoga membantu.