PLEASE HELP... PLEASE

So I am honestly not sure what THEY though when they did this.

Step-by-step explanation:

So when you look at this, we see that:

3x+3y=10

2x+3y=20

Lets just compare these two.

There is only two differences

There is 1 less x, or -1x in the bottom equation.

The number value is 10 more, or +10, in the bottom equation.

This must mean that -x=10

Or

x=-10

This is my way of doing it, their way of doing this is:

Combining the two equations 3x+3y=10 and 2x+3y=20

lets work through this their way and find our mistake.

So combining them we get:

5x-6y=30

Oh...

Well, I see their mistake, do you?

This is our equation:

5x+6y=30

Their equation:

5x=30

The difference is that they though they needed to subtract 3 y from 3y, canceling the two y variables out. When really, you need to combine the two y values.

So this is our REASONING.

Now, you cannot solve it this way further, since you have two variables.

However, using the method above, we were able to find that x=-10

Hope this helps! :)

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so: