Question

Solve, using the method of substitution

10% of x + 20% of y = 24, 3x – y = 20

Answer 1

`10/100 xx x + 20/100 xx y` = 24

`x/10 + y/5` = 24

Multiply by 10

x + 2y = 240 → (1)

3x – y = 20

– y = 20 – 3x

y = 3x – 20 → (2)

Substitute the value of y in (1)

x + 2(3x – 20) = 240

x + 6x – 40 = 240

7x – 40 = 240

7x = 240 + 40

7x = 280

x = `280/7`

x = 40

Substitute the value of x = 40 in (2)

y = 3(40) – 20 = 120 – 20

y = 100

∴ The value of x = 40 and y = 100