Could you explain how they solved it please?

Question

y=x-4 x=

6x-7y=21 y=

Answer 1

Madeline, they’ve given you a good start.

the first equation says that

y = x-4

so in the second equation, replace “y” with “(x-4)”

6x - 7y = 21

change it to:

6x - 7(x - 4) = 21

Now, solve that for x.

then substitute that value in place of x in the first equation, to discover y.