Answers

1.X + y = 60
x  - y = 30
60+30=90
2x = 90
x = 90:2
x = 45
x + y = 60
y = 60 - x
y = 60 - 45
y = 15
2. 10x + 2y = 5.400
5x + 4y = 3.300 x2=
10x+8y = 6.600
10x+2y = 5.400
6y = 1.200
y = Rp 200 (pensil)
5x + 4(200) = 3.300
5x = 3.300-800
5x = 2.500
x = Rp 500 (buku)
3. Keliling = 2 x (p + l)
p = l + 20
160 = 2 x (p + l)
160 = 2 x (l + 20 + l)
160 = 2 x (2l + 20)
160 = 4l + 40
160 - 40 = 4l
120 = 4l:4
30 = l
p = l + 20
p = 30 + 20
p = 50
4. 200x + 500y = 6.400
 2x + 5y = 64
x + y = 20
 x = 20 – y 
Substitusikan x = 20 – y ke 2x + 5y = 64 
 2(20 – y) + 5y = 64
 40 – 2y + 5y = 64
3y = 24
 y = 8
Substitusikan y = 8 ke x = 20 – y 
 x = 20 – 8 = 12

Jadi,banyaknya uang logam yang dimiliki anak tersebut:12 keping uang logam 200-san & 8 keping uang logam 500-san
5. Rp 300.000,00 + Rp 60.000,00 = Rp 360.000,00

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