Using substitution:
first you have to express one variable in terms of the other, in this we can express y in terms of x:

Since both expressions are equal to y, you have to equal both expressions like this:

Now you can solve the equation:

Knowing x=10, you can use any of the expressions we found before to find y. In this case I'm going to use y= -x+9 because it's simpler but boy should give you the same result

So, the answer is x=10 and y=-1
About 100. (Im not quite sure)
To know how many liters of water Bao use per liter of flour we have to divide the liters or flour so:

So Bao uses 0.33 or 1/3 of water per liter or flour
and to know hoy manu liters of flour Bao use per liter of water we have to made the oposite division so:

She use 3 liters of flour per liter of water
Step-by-step explanation:
REALLLYYY???!!!!!!
JK
thx 4 the points..