algebra substitution method with no coefficient of 1

http://i1209.photobucket.com/albums/...g?t=1333652905

I'm having trouble on number 25

I know how to use the substituition method if a variable has a coefficient of 1 or -1 but none of the coefficients here have that

can someone please show me how to do this.

Re: algebra substitution method with no coefficient of 1

You have to solve one of the equations for y, and it doesn't matter which one.

6x-7y=-4 (subtract 6x from both sides)

-7y=-6x-4 (divide everything by -7)

y=6x/7 + 4/7 Now you can substitute. Generally speaking Elimination would be a much easier way to solve this to avoid the fractions.