Question

How do you solve the system of equations `5x + 4y = 60` and `8x + 7y = 99`?

Answer 1

`color(red)(x = 8, y = 5`

Explanation:

`5x + 4y = 60, " Eqn (1)"`

`8x + 7y = 99, " Eqn (2)"`

`7 * " Eqn (1)" - 4 * " Eqn (2)"`

`35x + 28y - 32x - 28y = 420 - 396`

`3x = 24 " or x = 8`

Substituting value of 'x' in Eqn (1),

`5 * 8 + 4 y = 60`

`y = (60 - 40) / 4 = 5`